We stayed at Alex's apartment for a few days and it was absolutely fantastic.
Both Alex and his wife were extremely accommodating even though our check in plans kept changing.
The apartment itself is up several flights of stairs, then a circular metal staircase. While the climb can be a bit taxing with luggage, the construction is safe. The apartment offers fantastic views over Mexico city and the garden is really good to chill out and have some beers in.
The district itself was quite safe, even as blatantly gawking tourists.
We would definitely have loved to stay longer at this place!