I greatly recommend Alejandro's place. It is a nice location in that it is relatively near the main attractions in the city/the city center, but still quiet streets. I never felt unsafe at all. A nice perk is there is a really nice and cheap food cart right outside the door. Everything in the place is clean, the bathroom is high quality. Very spacious and comfortable room. Check in was easy, even though we did it at midnight. Alejandro responds quickly to messages, and speaks English fluently.
Overall, if I ever visit Mexico City again, this would be the place I'd want to stay. No complaints at all.