Mario's place is clean and great because it is close (walkable) to nearby restaurants, coffee shops, and bars. The area is safe, I walked most of the time unless I was going to a museum or somewhere that was further out. I suggest using Uber (cheaper) than a taxi. Mario will have a list of suggestions once you arrive, I suggest checking some of those out. You will have a great time either way. There is so much to see, do, and learn in CDMX.