I know the people who run this place (I think they are the owners). They're super awesome and accommodating. But beyond that, $2.99 aguas frescas and horchata (different stuff each day - they have a choice of 5 drinks a day I think) and it's so huge it lasts me two days! And, the best part is that they're all delicious. They make my favorite horchata. I usually only go there for drinks or for ingredients to make burritos at home.
They have fresh-made tortillas that you just need to heat up on a pan for a minute or so, and they're great! I also love their beans and Mexican rice. You can get meat there as well - it's like a whole butchery, and they have pre-cooked meats like a deli - and everything I've tasted has been great. Basically, I think this place is awesome and I'm so glad it's just down the street from me since I can get good quality Mexican food any day.
I've personally never tried their tacos, but I heard they're very cheap and taste good. It's on my list to try.
It's also a weird request that I ask but I always bring in their aguas frescas cups and lids and everyone who has been at the cash register has been fine with re-filling it without giving me a new one. That way I use less plastic.