Pittsburgh is a funny city. There are fantastic high end restaurants (e.g. Tamari, Spoon, 9 on 9, 11, etc...), but not so many medium-to-low-end restaurants. Well, La Feria is the clear exception. For $15 (or less) you can have an amazing Peruvian meal.
My wife and I are experimenting with vegetarianism (I know, we're missing out on a lot of yummy meals!), and La Feria is particularly great for us. They always have 2 veggie specials that are great. Last night I had this bean and pumpkin dish which was fantastic.
The atmosphere is pretty laid back and the staff are friendly, so for a quick and tasty dinner, this is the place to go.