The question often arises if Oaxaca City is accessible for persons who are mobility challenged, in particular, in wheelchairs. While the answer is both yes and no, we have begun to identify places which are either accessible, or, somewhat accessible with assistance.
This list is continually in progress, so all are encouraged to submit new information as well as send other suggestions and any corrections to
Several persons with mobility issues have mentioned the generosity of Oaxaceños in assisting them as it is needed. For non-Spanish speakers, in asking for help, the following phrases are useful: 
Puedes ayudarme por favor - Can you help me, please.
Puedes ayudarnos por favor - Can you help us, please.
Streets and sidewalks
Care must be taken on the rougher sidewalks to avoid tipping, and while there are cut-outs at the corners of many of the streets in Centro and in other areas, none of this can be taken for granted. 
Disabled Parking Permit: DIF, Calle Amapolis 1204 (Corner of Calle Sauces), Col. Reforma. Note that Mexico recognizes U.S. handicapped stickers/cards.  Place a card on the dash in front on the driver's side where it is easily visible through the windshield.
Oaxaca Experience Tours Director Omar Rito,9511852471 
Customized tours with an awareness of wheelchair needs, eg. a tour to Mt Albán with a guide who can arrange for an individual to be driven to the top in a truck with a manual wheelchair.
Museums and Public Buildings
Museo de Arte Prehispánico de México Rufino Tamayo Av. José María Morelos 503: Not easy to get into but the staff will come out and cheerfully carry in a wheelchair.
Oaxaca Lending Library Calle de José María Pino Suárez 519: The downstairs, which includes the book and DVD collections is accessible. Upstairs where some meetings are held is not.
Entertainment venues
Cinemax Located at the Macroplaza Shopping Mall (see under Shopping category). Wheelchair accessible.
San Pablo Cultural Centre Miguel Hidalgo (Av. Hidalgo) 907, Centro. Two steep steps at entry to the concert area, but staff will cheerfully carry someone in. Good wheelchair accessible washrooms.
Teatro Macedonia Alcala Av. de la Independencia 900, Centro: Staff persons can open a door just to the east of the main entrance, assist in entering the building up one 4” step, then access the theatre up two steep ramps. They will return after a performance to assist in leaving the venue.
El Asador Vasco Portal de Flores 10-A, Centro In the Zocalo, easy access
La Biznaga Gral. Manuel, Calle de Manuel García Vigil 512, Centro: Not wheelchair accessible but staff will lift a wheelchair over a large lip into the restaurant.
Casa Mayordomo Restaurante Macedonia Alcala #302, Centro: Ramp opening
Ciao Italia Trattoría y Pizzería Andrés Quintana Roo 219, Centro: Big lip to get in but helpful staff will assist to get a person in!
Los Compadres Restaurante-Bar Calle Lucero, #109, entre Armenta y Lopez and Fiallo
Café Bar del Jardín Portal Las Flores 10,Centro: In the Zocalo, easy access
El Pipe Corner of Constitution and Pino Suarez: Breakfast and Comida only
Hotel Parador de Alcala Macedonia Alcala #301, one step in.
Marisquería Neptuno Sucursal Conzatti: Valentín Gómez Farias 220, Centro: wheelchair accessible.
La Tlayuda Plaza Santa Domingo, ramp into the Plaza
Restaurante Las Quince Letras Abasolo #300, enter on the side
TresBistro Tres Bistro in the Zocalo. Elevator to the second floor and a ramp at the front. Very good wheelchair accessible washrooms.
Zandunga Restaurant, Calle de Manuel García Vigil 512, Centro, wheelchair accessible.
La Casa de las Artesanías de Oaxaca Matamoros #105, Centro: Wheelchair accessible
Macroplaza Shopping Mall, Cristobal Colon International Highway 2002,
Col. Sta. Lucia Del Camino: Ramp to lower level, ramp-ilke escalator to upper level. Stores all accessible.
Mercado Sánchez Pascuas  Porfirio Díaz #719. Centro: Spacious enough to get around with a ramp to get down to the lower level. 
Spanish Schools
Spanish Magic , Berriozabal 200 Centro Oaxaca. The whole place was easy to get into as well as having access to an indoor toilet . All staff were always making sure that there were offers of help if needed, and were very kind and patient.
Other Useful Information 
ATM machine corner of Humboldt and Calle de A Quintana Roo that was in a good safe wheelchair accessible space 
Public toilets on East Side of the zocalo .
The voltage in Oaxaca is the same as Canada and the US so electric wheelchairs can be recharged with a regular charger, so an adaptor is not needed.
Wheelchair rentals or purchases Rentals on Los Libres 500 or 600 block, for purchases, Medical Supply shops