I really like La Condesa. What stands out is the variety of fresh salsas on their salsa bar, and the great variety of tacos to choose from. I've had the shrimp, and a couple of different versions of their steak tacos. I've also had the mole chicken, which was great as well.
Service can be a little sketchy here, mostly because they're often very busy. But if you're in the area, it's a great place to try.