Agree with the preceeding posts. Located in a somewhat obscure neighborhood, you have to wonder where the mostly well-dressed and well-heeled clients come from in the middle of the day? We were lucky to get a table on a Monday afternoon without a reservation, it was bustling. The room is very simple, but comfortable, and you immediately get the sense the place is most concerned about what is on the plate. One thing we noticed is that the service is very good as noted below, and also works as a team. We had a couple of waiters, and if it looked like we needed something a manager would also stop by. (Note Not sure how much English is spoken there, if any).
I had a green chile soup with rock shrimp that was amazing (the place is serious about the soups and salads, which most people seemed to be ordering). Main dishes were about 150-220 pesos, which was justified by the care and quality of the experience. My wife had a nice duck breast, which is not that commonly served here.
Obviously, despite its location, this place has made its mark as part of the burgeoning foodie scene in Mexico City, at prices that reflect value compared to what you would pay in the the hotspots of Polanco or Roma for similar quality.