We stayed for 5 nights at Paco & María´s lovely home just last week. It was our first time in Mexico City and the location couldn´t of been more perfect. You could get a taxi just a few steps off their front door. A Metro Bus stop was also very close. Metro station was a bit further away (few blocks), but walking distance. Also near, a pharmacy and a convenience store. Every morning Yolanda gave us the most yummiest breakfast with fresh juice, fruit, toast, tea, coffee and a hot dish on ocassion. I hope you can try her "cordon blue chilaquiles" dish (our favorite). They have two lovely dogs who were just a delight to spend time with. Paco & María were so helpful with tips and recommendations to get around the city. They always approached us when they got home from work and asked us if everything was good, and made us feel like just at home.
As a side note...On our last day, Paco recommended a walking tour of downtown with a friend of his Gabriel from "Pata de Perro DF" (http://patadeperrodf.com/) which turned out to be our favorite day. We visited colorful markets (Jamaica and San Angel I think) had amazing meals (tacos de carnitas, spanish tapas) and had an insight on the architecture of the city by visiting various historic buildings we would of not gone to if it weren't for Gabriel. Highly recommended!