Javier's place is an excellent location. I was in town for a Indian wedding, which had events all weekend (Friday/ Sat/ Sun morning + night). I was able to walk to most of them in 20-30 minutes, not to mention all the best nightlife spots (both popular and more low-key). I also walked to Zocalo, the historic downtown, and it was a great way to explore. In addition, as it's just off the main street, it feels very safe to walk around at night.
The internet worked great and the filtered water in the kitchen was a life saver.
My only downside would be the shower is very small and the water pressure is poor. I'm guessing this is pretty common in CDMX. However, the shower was also very clean, so it being small didn't bother me. I'm also a large human (6'4").
Javier is very nice and speaks great english, which was great as I can only just about understand spanish... definitely not able to speak back! He even invited me out, but I had a few too many wedding events.
I would definitely go back, and I really hope I get to!