I can highly recommend Alejandro's place - as other reviewers have said, Alejandro is the loveliest and most helpful person, probably the most welcoming host I have ever encountered. The apartment is in a beautiful building with fascinating history and the interior is wonderfully decorated in a unique but very Mexican style. Alejandro helped me with recommendations of things to do, places to eat, and the history of the building and Mexican traditions that were taking place that day.
I hope to visit again next time I am in CDMX! Gracias Alejandro :)