Mexico City: Metro, Metrobús and the Merced problem
La Merced is the largest market in the capital and the hardest to approach by car. The Metro is the sane choice: Merced on Line 1 and Pino Suárez on Line 2 both put you within a five-minute walk of the wholesale halls, and the Zócalo/Constitución station on Line 2 is the better entry for the Sunday antiques and crafts stalls around Plaza del Empedradillo. Trains run from roughly 6am and are busy with traders from opening; aim to be on a platform by 6:30am on weekdays if you want aisles you can walk through.
Driving into the Centro Histórico is a false economy. Street parking around La Merced is scarce, informal and best avoided, and the estacionamientos that do exist off Calle Circunvalación and near the Mercado de Sonora charge by the hour with rates posted at the entrance rather than quoted in advance. If you are coming from Roma or Condesa, the Metrobús Line 4 to Teatro del Pueblo or the trolleybus down to Pino Suárez costs a fraction of a taxi and avoids the Eje Central crawl. I would book a hotel within walking distance of a Line 1 or Line 2 station and leave the car keys in the room.
For the Saturday Bazaar del Sábado in San Ángel, the picture flips: there is no Metro nearby, so take a taxi or rideshare to Plaza San Jacinto, or the Metrobús to Dr. Gálvez and walk fifteen minutes uphill. Arrive before 9am when dealers are still unpacking and the cobbled square is passable. Coyoacán's Sunday market around Jardín Centenario is easiest on the Viveros/ Miguel Ángel de Quevedo station on Line 3, then a ten-minute walk. Both are pleasant at opening and unpleasant by noon.
Oaxaca: walking the centre, combis to the outskirts
Central de Abastos in Oaxaca is a twenty-minute walk south-west of the Zócalo along Calzada de la República, or a short taxi ride if you are carrying purchases. It is enormous and at its best from 6am to 9am when the mezcal, cheese and chapulín stalls are being restocked and the aisles are navigable. The Mercado Benito Juárez and Mercado 20 de Noviembre, two blocks apart near the Zócalo, need no transport at all if you stay in the historic centre; go at 7am for tamales and hot chocolate before the tour groups arrive around 10am.
The famous Sunday market at Tlacolula de Matamoros is the one that rewards a plan. Buses and shared combis leave from the Central de Abastos bus bay through the morning, and the journey takes roughly forty minutes on Highway 190 east; private drivers from the centre will quote a round trip and wait, which is worth it if you are buying pottery or textiles. Leave the city by 7:30am. On the way back, the village of Santa María del Tule and its tree make a fifteen-minute stop. If you are staying outside the centro, choose a hotel with secure parking on Calle Niños Héroes or near the Auditorio rather than gambling on street spaces.
Note that Oaxaca's market days shift around fiestas, and during Guelaguetza in July the city fills and roads to the valley tighten. Book accommodation weeks ahead for that window and expect combis to run full.
San Miguel de Allende and Guadalajara: cars, lots and timing
San Miguel de Allende is compact enough that the Tuesday organic market at the Jardín Principal and the permanent Mercado de Artesanías on Calle Lucas Balderas are walkable from almost any centro hotel. What is not walkable is the approach by car: the town's cobbled streets are narrow, one-way and unforgiving, and long-stay parking is limited to a handful of lots on the periphery, including ones off Calle Salida a Querétaro and near the Fabrica Aurora end of town. Park once, on arrival, and walk for the rest of your stay. Buses from Querétaro run roughly hourly and take about an hour and a quarter.
Guadalajara spreads the load. Mercado San Juan de Dios, near Avenida Javier Mina, is a short walk from the San Juan de Dios light-rail station on Line 1, and the surrounding streets are dense with traffic from mid-morning. Mercado Corona, off Avenida Hidalgo, is five minutes from the cathedral and best reached on foot or by the Mi Macro trolleybus. For Tonalá and Tlaquepaque, take the light rail to Río Nilo or Central de Autobuses and then a local bus east; driving means hunting for space along Avenida Tonaltecas on Thursday and Sunday market days, when the town closes streets. I would use the rail and a taxi for the last kilometre.
Early starts matter most here: Tonalá's stalls are set by 7am and the good ceramics go in the first two hours. Summer rain arrives in the afternoon from June to September, so mornings are also drier. Winter, November to February, is the most comfortable season for standing around in market halls.
What I would book, and what to skip
For a market-focused trip, I would book a hotel within ten minutes' walk of a metro or light-rail station in Mexico City and Guadalajara, and inside the centro in Oaxaca and San Miguel de Allende, where walking beats any other option. Ask at booking whether the hotel has parking and whether it is charged separately; in San Miguel and Oaxaca's centro, on-site parking is the exception rather than the rule. Confirm check-in times against your market plan: an early arrival needs a hotel willing to hold bags before the room is ready.
Skip driving to La Merced, skip the Merced on a rainy Monday when the halls are slippery and half-shuttered, and skip Tlacolula if you cannot leave Oaxaca before 8am, because the coaches and the traffic both peak after that. Skip the big crafts markets on national holidays, when locals outnumber visitors and prices firm up. For a full picture of what is worth buying once you are inside, the site's guide to shopping like a local is the companion read. If you want a specific market day and do not have the details, ask the hotel reception the evening before; they know the local schedule better than any app.