This place is outstanding. I have gone there for almost 5 years now.
To start, they give you free chips with some of the best restaurant salsa that can be found in this area. I often ask to get a second cup of it to put on my food. They also have South American cocktails, but I've never tried them.
The menu itself has the usual suspects (chimichangas, tacos, etc.), but then, they will also have "dishes of the day", which will often be gourmet South American dishes. And at $7-12 a pop, these are some of the best prices for this kind of food one will find. My favorite is the rice bowl. It's a hearty mix of rice, green pepper, onions, and black beans, with an arepa and some lettuce served on the side. Never fails to satisfy and is a deal at $5.00.
The atmosphere is OK. They have fast food style seating, but there are also tables outside, which are ideal for people watching, or just hanging out. The food is brought out to you, but the rest of the meal is self service. No one goes to this place for the ambience.
So, if you want great South American cuisine at budget prices, come down to La Parrilla.