Start with the big city markets: La Merced, Sonora and San Juan
La Merced, east of the Zócalo in Mexico City around the Merced metro station on Line 1, is the city's largest wholesale and retail market and the closest thing to a total immersion in Mexican food. Go early, from about 7am, when produce arrives and the aisles are still passable. Buy: dried chiles by the scoop (pasilla, guajillo, chipotle), fresh herbs sold in fat bunches, and mole paste by weight from the molcajete stalls. Expect to pay modest prices and to be pushed gently along by porters. Not a place for a leisurely browse on a Saturday.
Mercado de Sonora, near La Merced, is the famous herb and folk-art market: dried flowers, herbal remedies and piñatas. It is fascinating but not a food-shopping stop, so pair the two only if you have a couple of hours. For a calmer, more manageable food market, head to Mercado San Juan in Colonia Centro, a short walk from the San Juan de Letrán metro. It is smaller, pricier and full of restaurant buyers — good for exotic meats, truffles and a sit-down lunch at one of the fondas inside. I would book a hotel in Centro Histórico or Roma Norte for this, both within a 15-minute walk or a short metro ride.
Oaxaca, Puebla and San Cristóbal: the markets worth planning a trip around
Mercado Benito Juárez in Oaxaca de Juárez, a block from the zócalo, is the one to build a morning around. Buy: quesillo (string cheese), tlayudas, chapulines by the bag, and Oaxacan chocolate ground to order at the molinos. The adjacent Mercado 20 de Noviembre is where you eat — smoky pasillo de humo stalls sell tasajo and cecina grilled to order. Oaxaca's high season is November to March and again around Day of the Dead in late October; hotel rates in the centre rise then, so book well ahead. A room near the zócalo or on Calle Macedonio Alcalá puts you within walking distance of both markets.
Puebla's Mercado Hidalgo and the smaller Mercado de Sabores on Avenida 5 de Mayo are where to try mole poblano and cemitas. San Cristóbal de las Casas in Chiapas has a compact market just off the main plaza where you can buy coffee from the surrounding highlands and local honey. Both cities are high-altitude and cool at night, so pack a layer even in summer. If you are comparing bases, I would book Puebla for architecture and food, San Cristóbal for indigenous textiles and coffee, and Oaxaca if you want one market town to do properly.
Grocery stores and supermarket chains: what to buy and what to skip
For everyday supplies, the big chains are Soriana, Chedraui, La Comer and Walmart de México, with OXXO convenience stores on almost every corner. La Comer has the best fresh produce and deli counters of the big chains; Chedraui is the reliable middle ground in most cities. Buy drinking water in large garrafón bottles rather than small ones, and look for local fruit — mango, papaya, mamey, guanábana — which is cheaper and better in season than imported apples. Skip the imported cereals and packaged snacks; they cost more than at home and add nothing to a trip.
Farmers' markets, often called tianguis, rotate by day and neighbourhood, and most towns publish the schedule. In Mexico City, the Saturday Bazar de San Ángel and the Sunday organic market in Roma Norte are good introductions. Bring cash in small notes; many stalls do not take cards. A reusable bag is useful, since plastic bags are restricted in several states. If your hotel has a kitchenette, a market breakfast of fruit, bread and coffee costs very little and is often the best meal of the day. Book a hotel with breakfast included if you would rather not shop on your first morning.
When to go, how to get there and what to skip
Markets are best on weekday mornings between about 7am and 10am; weekends are crowded and some stalls close early. Most central markets are a short walk from a metro or bus stop, and taxis from hotel districts are inexpensive. Note that Mexico City restricts some car traffic on certain days under its Hoy No Circula programme, so confirm before driving. If you are arriving by air, Benito Juárez International is about 30 to 45 minutes by road from the centro depending on traffic; book an airport transfer or use the authorised taxi counters.
What to skip: the tourist-oriented souvenir stalls inside the big markets, where prices are higher and quality similar to what you find outside. Skip anything sold as a cure or remedy unless you know exactly what it is. Skip pre-cut fruit from street carts if you have a sensitive stomach; whole fruit you peel yourself is safer. And do not try to see three markets in one day — pick one, eat there, and walk. For accommodation, hotels near the centro histórico in any of these cities put the markets within reach on foot.