I live in Vegas and I always enjoy going to Firefly. It is my go to place to take people who come to town to visit. There is a varied menu of tasty tapas with something for everyone. Get a pitcher of sangria or mojito to really make things fun. My wife and I have a handful of things that we enjoy, but after coming here many times with various people with different tastes, I have not had a bad dish here. You can get out with a cheap lunch without drinks, but it is still reasonable for a full night of dinner and drinks.
Firefly is packed late night, but if you can manage to get a seat it's a great late night snack.