I love this hostel in downtown CMDX - very relaxed environment, great location, and good value for money.
It's basic - no coffee, no windows, a little dusty in some corners, clearly a high turnover on the rooms - but totally serviceable. The shower was amazing and the WiFi worked well.
I was in a sticky situation with my accommodation in the city and I was able to book, travel, and check-in all within an hour.
Check out the Lucha Libre show at Arena Mexico while you're here - it's right across the street.