Nice roundup. A few random thoughts and questions.

(1) Xochimilco - I finally made it a few years ago, only to find that the floating gardens were made of plastic flowers. I was really surprised (of course, it didn't ruin the day).
(2) The Metrobus - how do you buy your fares? They don't take cash onboard, correct? Where can you buy a fare card?
(3) Street food - be careful. It can be delicious. When you walk through Chapultepec Park and see all these beautiful cut fruits, and see the knives they use to cut them, either sitting in or being rinsed from, buckets of stale water, you really want to avoid any of these items, and in fact, pretty much anything that isn't cooked.
(4) The availability of UBER has really improved the quality of visits for the traveler taking safety precautions. I used to stay in a neighborhood where I'd either want to be going out for the night, or make sure there were quality hotels nearby so there would be a Sitio available (as to avoid street Taxis).