One of my two favorite Mexican places in the Chandler/Gilbert area. El Palacio in Gilbert and this are the two I go to most. I argue with myself over which I like more, each time I visit one of them..
Si Senor's has awesome green chili! To be honest, I haven't tried too many of their other items. I had their green chili there my first time a few years back, and when I stop in again I crave it so bad that I just end up ordering it again. I kind of alternate between their spicy green chili and their mild green. My dad likes their red too, I'm just not a fan of red in general. Sometimes their green mild is pretty hot, and sometimes their spicy green is so hot I have tears and snot running down my face (if you like heat, you know this is a good thing). Although when it is that bad, I usually cry all the way home and promise to never get the spicy again. Then a visit or two later I forget and order it again.
Salsas/bean dip/chips are always great. You get a round of sopapillas with honey free at the end of every meal. Love the food and I always have leftovers for later.
The one thing I don't like is it is always very crowded and with a busy place comes noise. Clearly many people also know how good it is, so if you don't get there early it can get loud and the seating is a little too close for my taste in general (but nothing obtrusive). But when it is less busy and you can sit back and enjoy and eat your green chili and cry spicy tears it is about as good as it gets.