During my years in Boston, this was my favorite place to eat hands down. Cheap, good Tex-Mex/Cajun food. The lines tend to be long (no reservations accepted) and the place is pretty noisy, but the food is good.
My favorite plate is actually an apetizer--quesedllia with avocado. Huge slices of avocado cooked right in the tortilla and cheese. The fajitas here are very good too.
WARNING: As much as I love the place, a friend of mine hated it. Not so much for the food, but he said the palce was a health inspector's paradise. He happened to work above the place, so he may have had a good perspective of things. That doesn't keep me from eating here though when I have the chance.