Don't be afraid of the complex, it looks a little shady from the outside, to be honest it is not that nice inside either. However more often than not the hole in the wall joints turn in to hidden gems. This isn't exactly a gem, but it is cheap and good (say Los Favritos or La Salsa kind of good).
The tacos are great and so are the tortas, the meat gets simmered for hours and the veggies are always cold and crisp. Ask for the extra hot salsa, it is smoky and spicy and wonderfully flavorful, I think it is chipotles en adobo but I can't confirm this.
If you happen to find yourself on the southside and are in the mood for fast, cheap mexican this is the spot to hit.