I have eaten here twice now for lunch. The first time I had the Cajun burrito and the second time I had the Xel-Ha burrito, both $8.56 with tax. I was pretty satisfied with both. The Cajun burrito has shrimp and steak, and the Xel-Ha has a choice of meat. I ordered the Xel-Ha with hot salsa, it is was probably the spiciest Mexican dish I have ever had. It was almost like Thai food.
The interior is pretty nice with windows looking out over market square (well, not such a nice view until the city finishes construction). The roof is essentially one giant skylight, but they keep it covered during the day.
Service was good and it is a good price for lunch (dinner is much more expensive though). Their menu is online if you would like to see more. I prefer this place to the Mexico City restaurant.
* all major credit cards including Discover accepted here*
Food Quality/Taste = 4 Stars
Portion Size Given Price = 3 Stars
Relative Price = 4 Stars
Service = 4 Stars
Experience with Staff = 4 Stars
Decor = 3 Stars
Clean (yes/no) = yes