As others have said, you MUST order the taco adobado (or two, or three). The meat is carved from a giant skewer and is perfectly seasoned. Order it with everything ("con todo"). FYI, this is NOT a spicy food.
Tried the carne asada- only average. If you're adventurous try the tongue ("lengua") or other useful animal parts (I didn't, so mangiador emptor).
Don't be intimidated if you don't speak spanish- they're used to gringos. Take the walk- it's good for you and definitely worth it.