Casa Barcelona! -->IS SPAIN THE NEW FRANCE?
Casa Barcelona is a great place to go with a crowd. Much of their menu is in the form of tapas (everything from meats, seafood to many veggie dishes) and I would recommend going that route rather than ordering their dinner plates. The food is varied, generally mild but quite flavourful, and if you like sangria with lots of fruit in it, this is your place. I believe they specialize in particular regional cuisine, but I can't tell you which - all I know that, according to my friends who recently visited Madrid, their food is quite different from what they experienced.
I would not say that Casa Barcelona is cheap. If you order a bunch of tapas, you may run the tab substantially, especially since the tapas do vary in price and some portions are small. So I would say it's more mid-priced.
The place itself has a very nice vibe, call ahead to find out on what nights they have flamenco dancers (last time I went I lucked out and saw them, and they were captivating). The owner is quite sweet, he comes around to all the tables to see how things are, and likes to chat. I recommend it.