On Midway Drive, a mere ten minutes by car from one of San Diego's most famous attractions, Seaworld, you'll find a branch of one of California's most popular fast-food restaurants: Taco Bell. A byword nationwide for cheap and, er, cheerful Mexican fare since the 1950s, it currently sells the likes of the 'Doritos Cheesy Gordita Crunch' and the 'Double Decker Taco Supreme' to cash-strapped college kids and hungry families who have quite possibly never set foot across the border.

A town called TJ

Just 20 miles south of that branch of Taco Bell is the border town of Tijuana, in the sunny Mexican state of Baja California. A not-especially-attractive conurbation with a population of more than 1.5 million, for the past few decades it's been cursed with the type of reputation that makes even Donald Trump look palatable; riddled with drug cartels, frequent gun battles, cheap prescription drugs and rowdy springbreakers.

But the city has undergone a transformation in recent years, with a crackdown on crime and a new generation of enthusiastic young entrepreneurs embracing the food-truck and craft-beer scenes, who refer to their hometown as 'TJ' – and its stature as a destination for fantastic food is soaring. For one thing – and this might surprise you – it's home to that most ritzy of menu items: the caesar salad.

Yes, here, in a restaurant on the once somewhat sleazy main artery of the Avenida Revolución where underage, sombrero-wearing students would come and party, head chef, owner and Italian immigrant Caesar Cardini knocked up this snack in 1924 for a guest from some leftovers. Today, you can still order it from an immaculately clad waiter sporting a spotless, ankle-length white apron, who will prepare the dish tableside with fresh, crisp romaine lettuce, olive oil, ground mustard, grated parmesan, baked croutons and anchovy fillets in an elegant piece of restaurant theatre.

i want to erase the perception people have of 'typical' Mexican food

Caesar's is a little chunk of history – the restaurant still has its original, long, polished wood bar and 1920s espresso machine – but its current co-owner is a man who has been doing much to revitalise not only Tijuana's food scene, but the city itself. Local chef Javier Plascencia has grown up around cooking and restaurants – his father, Juan Jose, started his own pizzeria in the city in 1969, and the family now own several dining establishments. In 2011 he opened Mision 19, a stylish restaurant which uses modern techniques such as cooking sous vide, and which has already won several awards. A year later, he persuaded the city's mayor to create a zona gastronomica in an area downtown, in which several good restaurants now thrive.

Five more to try in Tijuana

La Querencia: Chef Miguel Angel Guerrero calls his style of cooking ‘Baja Med’, blending the ingredients from the Baja coast with those from the inland, which has a more Mediterranean climate. Avenida Escuadrón 201; laquerenciatj.com

Maquina 65 at Telefonica Gastro Park: Don’t miss the outrageously good octopus hamburger or the duck and cheese taco at this food truck. facebook.com/maquina65

La Caza Club: Funky, design-led restaurant where talented chef Ruben Silva serves up local flavours like pork cheeks with avocado, cheese and cucumber. Miguel Alemán Valdez; facebook.com/lacazaclub664

The Food Garden: A modern, hawker-style food-hall with dozens of outlets; Javier Plascenias’s Erito serves obscenely good ensenadas de pescado (fish tacos). Plaza Rio; facebook.com/foodgardenrio

Fauna: Laid-back, quirky bar and tasting room in Tijuana’s craft beer ‘district’ around the old Plaza Fiesta, offering dozens of locally-brewed beers. Paseo de los Héroes, Plaza Fiesta; facebook.com/faunatastingroom

"I couldn't have opened this 15 years ago," Plascencia admits frankly from the dark wood and red-accented dining room, situated on the fifth floor of a slick office building downtown. He's referring not only to the period when cartels scared away tourists as well as intimidating locals, but to his adventurous and sophisticated cuisine, which now appeals to adventurous and sophisticated diners. One thing he is passionate about, and proud of, is only using local ingredients; a thread which runs through the cooking of all the chefs I meet. "I want to erase the perception people have of 'typical' Mexican food – we've got more to offer than burritos and enchiladas," he says.

Plascencia likes to combine unusual flavours, demonstrated by dishes like foie gras with candied olives, red wine sauce and roasted apricot, or roasted beet salad with pickled carrot, grapefruit jam, pistachio, lentils, beet leaf pesto and goat's milk cheese. I try the tasting menu – incredible value at £28 for seven courses (£39 with wine). Standouts include intense, salted bone marrow with a fiery tomatillo and habanero sauce; meaty, chargrilled octopus with pistachio, elephant garlic, and chickpeas; and the carrot bread pudding with a pretzel and sweet milk gel – like the most heavenly, creamy and crunchy bread and butter pudding you've ever had.

The next morning, I stroll around the city's busy, chaotic and traditional Hidalgo market, where chefs and housewives alike have been flocking for decades to buy pre-prepared mole pastes in varying strengths and sweetnesses, choose from hundreds of different types of dried chillies, or squeeze fruits such as persimmon, passion fruit or soursop for ripeness.

I stop by El Jerezano, a sit-in stall where I sample the small but smiley owner Josefina Marquez's gordita de chicharron con salsa rosa – deep-fried pigskin, a local delicacy, which you'll recognise if you've ever had pork scratchings – before bracing myself at another stall, La Oaxaqueria, to try a hearty bowl of…grasshoppers. Known here as chapulines, they come seasoned with lime and salt. To my surprise (and relief) they're just crunchy, and worryingly moreish.

Later, I head to the Telefonica Gastro Park, located next to an old telephone exchange, which currently features around 15 different food trucks all serving interesting twists on Mexican food; by lunchtime, regulars and office workers are already filling up the communal bench seating. Passionate, tattooed twentysomething Tijuanan Jose Rodrigo Figueros Sanchez spent several months working for acclaimed chef Simon Rogan in the kitchen at L'Enclume in Cumbria, before deciding to go it alone with his truck, Carmelita, named after his grandmother. "I use traditional Mexican ingredients to cook the kind of thing my grandmother would have, but with very modern methods," he explains.

I try his roasted cauliflower taco with homemade mole (his features 32 ingredients; more basic ones average around 15), which is earthy, smoky and just a little bit sweet, before biting into a slab of beef tongue torta, the meat utterly tender and surprisingly light, lifted by a sharp salsa. "For me, and the other guys here," he explains, "this is a way to gauge the reaction of our customers for a smaller investment, then hopefully one day open a restaurant of our own." I admire his ambition, and I hope that by the time I return, he – and the others like him – will have made their dreams come true.

The Holy Trinity

In the heart of the sprawling metropolis that is Mexico City, not far from the stately, forested Chapultepec park, is the smart, upmarket neighbourhood of Polanco. Its wide, Bond Street-like boulevards are lined with designer stores, from Gucci to Tiffany, and, fittingly, it's also home to the triumvirate of first-class restaurants that made it onto the World's 50 Best Restaurants list in 2015, including Pujol (16), Biko (37) and Quintonil (35), overseen by chefs Enrique Olvera, Mikel Alonso and Jorge Vallejo respectively.

In Biko's airy, first floor dining room, over a starched-cloth-covered table, the salt-and-pepper-haired, Basque-born Alonso is enthusing about the current Mexican food scene. "There are so many exciting restaurants here, not just in Mexico City, but in the whole country," he says. "The world is getting to know that Mexico is a great place to eat, which is a great thing for us." He studied at San Sebastian's Luis Irizar Cooking School before moving to Mexico 17 years ago with friend and fellow chef Bruno Oteiza; the pair opened Biko together in 2008.

Their signature techniques – a mix of complex and playful – result in dishes like foie gras mousse with pineapple, a chlorophyll and anise foam, and edible begonias, or chocolate 'soil' with toasted amaranth, coffee and cookie crumbs. The house mole is aged for months, so the flavours develop in intensity – diners are even informed how old the current base is when they order it. "I want people to know that Mexican cuisine is some of the most complex in the world, that it's worth the journey," he expounds. His seven-course tasting menu (£39 without wine, £76 with), encompasses seasonal ingredients, producing picture-perfect, highly Instagrammable plates of food which in some cases are almost too pretty to eat, but which definitely don't skimp on flavour.

A few streets away, local boy Jorge Vallejo is overseeing his busy kitchen at Quintonil. Front of house, the décor is fun, with astroturf on the walls, the atmosphere less formal than at Biko. After culinary school and a stint on cruise ships and in hotels, Jorge honed his trade working for mentor Enrique Olvera. He then made something of a pilgrimage to Copenhagen to work alongside culinary hero René Redzepi of Noma ("I wanted to see how the best restaurant in the world works," he explains), before opening this restaurant with his wife, four years ago.

His philosophy is straightforward: "We use ingredients which are perhaps a little unusual or underrated," he says, "but I like to make something spectacular out of them, and also make them taste fresh and light. They are things you find in small towns, mostly in peasant cuisine, like cactus or ayocote beans, but I find it more challenging and rewarding to make something special out of something simple than out of ingredients like caviar." I have no hesitation in attacking his popular seven-course set menu; everything is so delicate, so balanced, that by the end there is no bloating, no heaviness, no carb coma. I especially loved the zingy, green cactus ceviche with samphire; the smoked crab tostada with habanero chilli mayo and radishes, which had a just-out-of-the-sea, citrusy freshness; and a sweetened corn crumble pudding with a lemongrass panna cotta, which basically tasted of Thailand.

Mexico City

Pujol

How about a tostada with powdered ants, coffee and sweetcorn? Or a dish of fungus, liver and chicken gizzards? It’s testament to chef Enrique Olvera’s genius that these basic, icky-sounding ingredients taste like heaven. Calle Francisco Petrarca; pujol.com.mx

Fonda El Refugio

This colourful, family-run inn has been dishing up Mexican favourites like chiles rellenos (chillies stuffed with ground beef) and chicken in mole sauce to loyal diners since 1954. Calle Liverpool; fondaelrefugio.com.mx

Paxia

Hotshot chef Daniel Ovadia, who owns several restaurants, wows with quirky dishes like deconstructed tortilla soup and serves mini-wagons of mole sauce. Avenida La Paz; paxia.mx

In a city known for its street food, with hawkers on every corner selling freshly squeezed cactus juice, griddled tortillas with cheese and meat fillings, or simply grilled ears of corn, chefs like Jorge and Alonso are taking inspiration from their roots and elevating it to another level. Combined with the incredible art which runs through Distrito Federal's veins – vast, striking murals by Diego Rivera, knowing self portraits by Frida Kahlo, colourful trees of life at the folk art museum – it's definitely a place to come and really whet your appetite.

Earthy flavours

A 45-minute flight from Mexico City is the elegant, colonial town of Oaxaca, capital of the state of the same name (and which gave its name to Thomasina Miers' Wahaca chain). Ringed by mountains, this Unesco World Heritage site is a feast for the eyes – its Spanish-style buildings are painted in a rainbow of shades, from electric blue to egg-yolk yellow, while every other market stall proffers fabrics and garments in neon pinks, forest greens and tomato reds – as well as the tastebuds. The diverse and delicious Oaxacan cuisine is lauded through the country – the state even has seven signature mole recipes, from intense, dark mole negro, to the sweeter mole almendrado, made with almonds.

Just walking through the vast, teeming 20 de Noviembre food market beyond the central zocalo, or main square, will make your mouth water. At its entrance, you run the gamut of the grilled meat section; dozens of stall-holders tend to their smouldering, red-hot coals, offering different cuts and types of meat, which you choose, before selecting a range of vegetables to accompany it. Further in, hawkers are preparing fresh tlayudas – their equivalent of pizza – huge, crunchy discs of fried or toasted tortilla, topped with local cheese, salsa, shredded meat, lettuce and avocado. Here, chefs and home cooks alike make the most of the bounty of ingredients they have on their doorstep.

One of them is Aurora Toledo, the matronly chef-owner of Zandunga, a brightly decorated eatery which dishes up hearty, local fare. Like many Oaxacan bars and restaurants, Zandunga has an extensive list of mezcals, the smoky, agave-based spirit native to the region. "I drink it medicinally," she laughs throatily when we meet; "it's good for the throat!". Her signature dish is estofado, a long and slow-cooked beef stew cooked with habanero chillies, tomato, onion, achiote paste and coriander, sweetened with apple and pineapple. It's fantastically rich, and is so highly prized it's often served at weddings. "We're so lucky, here," she says, "we have such a wide variety of flavours, and our food has texture, colour, and history." She calls herself a cook, rather than a chef; self-taught rather than trained, she focuses solely on traditional food, without any twists.

Those who have studied at culinary schools can rightfully call their cuisine cocina de autor, or 'cooking by auteur'. At Pitiona, one of the town's most lauded restaurants, I meet chef Manuel Rodriguez. He studied in Spain, where he learned many techniques including cooking with liquid nitrogen and spherification (shaping a flavoured liquid into a gel-like sphere). Here, in the relaxed surrounds of the pale-walled dining room, there's a bit more drama to the dishes.

Getting there

British Airways flies to San Diego from approximately £612 return, or to Mexico City from approximately £850 return, visit ba.com for offers. AeroMexico flies direct to Mexico City from £570 return. Fly on to Oaxaca with InterJet, which offers return flights from £80, interjet.com. Budget-conscious travellers may prefer to take a luxury coach, prices are reasonable – try Ado Platino, ado.com.mx. For more information on Mexico, see visitmexico.com.

"There's lots of innovation going on in Mexico at the moment," confirms Rodriguez, "and here we combine the traditional with the innovative." I slurp his sopa di fideo, a tomato and beef broth containing spheres of local cheese which explode on my tongue, making it taste like the most comforting soup in the world. This is followed by red snapper, served under a bell jar, which is lifted theatrically to release the smoke that has flavoured it during cooking. It's been cooked with plantain and chayote – a green, fibrous local vegetable – and topped with spicy chile de agua. The piece de resistance is rice pudding, prepared at the table; the milk, sugar, rice and cinnamon concoction is squeezed into a bowl of liquid nitrogen so it makes a hard, crunchy, meringue-like dessert, served with a jug of hot chocolate. It looks very impressive, and tastes just as good.

My foodie crusade has been a veritable voyage of discovery through a range of flavours, techniques, ingredients and interpretations; trust me, you'll never look
at a burrito the same way again. ■