Rude staff, overpriced food.
On my first visit to Mad Mex, it was early Saturday night. We were a group of ten looking for a meal, and were promised a twenty minute wait time. We still hadn't been seated when we left two hours later. The manager was waving his arms and saying it wasn't his fault, and that there's nothing he can do.
I did give them another chance. I went with a friend on a Monday evening. It was a quiet night and we didn't have any trouble getting seated. The waiter was lethargic, and couldn't answer the simplest questions about the beer or the food menu. The food wasn't anything special, and overpriced for what it was.
My third visit was for drinks in a small group, on a weeknight, perhaps a Wednesday or a Thursday. We were sitting at a table. It was a quiet night, yet we had to keep walking to the bar to tell the staff to find our waiter and send him to our table, over and over again. Even though it was over an hour before closing time, staff kept working with their rags and vacuum cleaners all around us, and making faces like we should consider leaving soon.