If you know you want to spend some time staying near the historic center of Mexico City (and whether you do or you don't, as opposed to staying elsewhere and visiting downtown, is another story entirely), then this might very well be the place. It's HUGE (three bedrooms, dining room, living room) and it's quiet - nothing to sneeze at when you've been out and about in the hustle all day. WiFi was awesome, for working and relaxing. There's a good-sized fridge for your drinks and to house the makings of an occasional break from tacos and other street food. (Though I recommend sticking with that for the most part.) Pick up ingredients for a home-cooked meal at the very-nearby Mercado San Juan. Take home momentos of Mexico from the even-nearer-by Ciudadela market. Walk the Alameda every night to see how life is lived in the big city. (But hands off my favorite cantina.)
As others have noted, it's an odd neighborhood. The immediate blocks are filled with single-item hardware stores, which makes for purely-commercial mornings and afternoons that I find pleasantly "local", though it does mean going at least a couple of blocks for any real food and drink options. Come closing time (6 or 7?) the whole place shuts down. It's super quiet and almost abandoned for the next few hours and then, yes, some use that as a chance to get some sleep on the sidewalks. I found this not at all alarming, though on one Saturday night, when I was already inside the gated door on the ground floor (the apt is up one flight and toward the back), the kids banging a soccer ball loudly off the all the other metal shutters - it would have been somewhat disconcerting had I wanted to leave at that moment. In general, I'd say you get used to the rhythms of this particular neighboorhood.
I'd also note that the hot water didn't last very long (I never had enough need of it to raise the issue with Marcye; cold have been me, or something fixable), and I concur with an earlier review that it's a little weird to have locks on both the apartment front door and the metal door from the street that are operate only by key. How do you get out in case of emergency, should you lose the key?
That said, the price, location and comforts of the apartment itself make this a likely return destination for me next time I'm in town.