Go early in the day, unless you don´t mind things running out. This is a very popular place selling carnitas and barbacoa, the specialties of the house.
There is the restaurant area and also the zone for the "to-go" orders, we always prefer to eat at home, as you can have a more relaxed time and you make your own environment and choose your companions.
This place started as a stand in the sidewalk, but became so popular that they grew into a big 150-customer restaurant with full service. Their menu is not that varied, but offers you more than the carnitas and barbacoa, and they serve beers and a few other alcoholic beverages to go with your tacos while you watch TV, normally a soccer match or wrestling.The fact that they are close to Coyoacan means that a lot of the customers buy their meat "to-go" and eat at home or maybe a little "party" at the office at lunchtime, so their busiest section is the one in the back of their parking lot. There you can buy by the kilo. The price is not exactly cheap, but their quality backs their fame. If you go on a weekend at lunchtime, it would be a sad experience to return empty-handed, because they may have run out of barbacoa.
A little parenthesis on Barbacoa. In Mexico, it is not synonymous with BBQ by any means; here a barbacoa is a specific dish, normally lamb cooked in an underground earth oven, with the meat wrapped in maguey leaves places in a big pan over hot coals and big slabs of stone, then covered with more maguey leaves and soil. The package is left to slowly cook for many hours, maybe even overnight, and then it's ready to eat. The result is very, very tender meat that will almost melt in your mouth. The juices of the meat were collected on the pan and are served as a consome. You add some lemon, chopped onion, and cilantro, and they are good to enjoy with the company of fresh tortillas. Barbacoa are normally served only on weekends or big holidays, due to the prep they require.