Similar to Los Betos - Fiesta is decent inexpensive mexican food. The staff is nice and accommodating. I did have a pretty hilarious conversation with the girl at the counter though... I was trying to order my burrito without onions, and she kept saying "okay" and "yes" and nodding at everything I said. I would ask her questions and she would say "yes" and press buttons on the register. It took me a few minutes to realize she had absolutely no idea what I was saying.
Aside from that, my burrito wasn't bad... nothing special though. The beans were from a can, the guacamole wasn't fresh (I doubt anything was), everything is cooked in or made of lard, their chips are flavorless and kinda stale, and they are seriously lacking any sort of salsa. They just have the typical generic nameless hot sauce found in these joints.
As I said - Los Betos... but cleaner and a little better maybe. It's just a place for convenient late-night munchies.