I only go to Mad Mex for two things: $7 Big Azz Margaritas from 9 pm to midnight and half-off food from 11 pm to 1 am. The Mex earns a spot in the lineup for 21st birthdays and other occasions that merit bar-hopping and all-night drinking (e.g. midterms, breakups, Tuesdays).
The food is consistent and tasty, though not exactly the most authentic Mexican food ever. There are lots of option for vegetarians and even vegans. I have to eat gluten-free and they've always been accommodating and knowledgeable. Free chips and salsa at the bar is nice.
Why does this place get 3 stars instead of 4? Couple reasons:
1. Stupid policy of not serving alcohol if there are people under 21 at the table. Sucks when you're out with your underage friends and want some tequila with your enchilada.
2. You won't get a table during peak hours unless you're ordering a legit meal. Nachos to share don't count. Which leads me to...
3. Super crowded. Very difficult to get a seat at the bar on busy nights.
Also, one little weird complaint: the bar is sloped and uneven, so it's VERY easy to have a bowl of salsa or even your drink (dios mio!) slip off, particularly once you've had a few.