Can't believe I haven't written a review yet.
This place has the best Mexican food I've found so far in Madison (I've had better elsewhere, but it really is quite good for serving white bread Wisconsinites) and they are quite affordable!
SO sticks with the Lomo de Puerco en Salsa Verde every time, tender with a nice heat. I jump around and have tried a variety of taco, burrito, quesadilla, and platillo combinations. I recommend pork for your choice of meat, flavorful but not tough or stringy. Definitely try a horchata, Mexican Coke, or Jarritos with your meal. Tamarind Jarritos is my favorite.
The place is small, with a pick up spot and small counter in front, with maybe 10 tables in the back. I recommend an early lunch/dinner especially if you want a meal on the weekends (!!) so you don't have to wait in the cramped space up front (the line extends outside even during winter..). Thankfully food comes out pretty fast and you get free salsa and chips to curb your hunger pangs.