We spent a substantial portion of our holiday budget on tourist taxis. This was mostly arranged by the hotel, and at times by an eager bellhop. Roughly, we spent 2x-3x on taxis than on meals. No, make that 4x. The one time we asked a cop to help us locate a cab, he flagged down a passing Nissan. It was when we got on that we realized how overpriced our hotel arranged cabs were compared to the "sitio" taxis. But with a little baby in our hands, better safe than sorry.
Mexico City is one of the most vibrant and artistic places in the world I've ever seen. There is art and culture wherever you look - even in the poorest of poor migrant basket weavers. We would return in a heartbeat. Hell, we would move there if I could find a relevant job.