I love Barrio for a quick bite - the tacos are cheap and the margs are good. Although sometimes it's not "quick" if you go at prime time and have to wait for a table, but we live nearby and are usually there on off days.
The service is usually the downfall of this place - the servers are nice enough but are usually forgetful and can be a bit slow. So if you're there on a Friday night, you'll need to be patient. I recommend sitting at the bar if you're with a small group, you'll get better attention. Just my two cents.
The build-your-own taco concept is fun and Barrio offers a lot of delicious options. The tacos are so good you feel like you're stealing them for $3, but that's why I love it. It's a great value and a really tasty night out. That said, we are repeat customers!