Franciso's place is great- HIGHLY recommended. It's conveniently located, walking distance to Bellas Artes and Zocalo. Tons of places to eat right around the apartment, including a fabulous vegan place called Super Soya- cheap, great salads, great food.
Franciso is amazing. Very responsive, helpful, gave us a great list of places to check out (and it's got some things on there we would never have gone to on our own, like the poliforum!). On our last night, there was an earthquake, and within minutes, I had a text from Francisco checking on us. That's the kind of guy he is... thinking of others and making sure his guests are comfortable.
Can't go wrong with Francisco's place!