Im originally from chicago but am living in barcelona now and have been for the last year. a few uggestions:
a nice cheap lunch spot where you can get 1.50 sandwhiches and 2 euro bottles of cava. still good quality street food and a local favorite. no seats, its a stand up bar and is bound to be packed any time of the day. Its in the barceloneta neighborhood and is called Chapagneria. I reccomend the entrepan de chorizo, queso, y cebolla, and a bottle of Rosat for about 3-4 euros in total.
Takeaway catalan rotiserie chicken. On the corner of urgell and aragon.
Menu of the day- argentinian brasserie with an excellent selection of grilled meats from galicia and argentina. It is tucked away in a small alleyway right of the corner of bruc and trafalgar. on trafalgar there is a samll alleway with shiny metal letters that say "Passeig". Go for lunch to get one of the best values in town but get there before 1:30 to avoid a long wait. the menu changes daily, but the selection of meats always provides good options. Try the solomillo de buey
Argentinia empanada joint on torrent de lolla in the famous neighborhood of gracia. Try the ternera milanesa and an empanada de carne picante. they deliver too.
Paco Meralgo -a little more upscale, but with high quality traditional catalan cuisine and an assortment or mariscos, or shellfish, in tapas portions. still reasonably priced on calle muntaner, I believe between corsega and rosello.
Bar Inopia- calle tamarit and roquefort. a nice tapas bar with limited selection but with excellent tapas and a nice place for drinks. It is run by the brother of the famous adrian ferran, owner of el bulli, known as one of the worlds best restaurants. Try the grilled tuna, the lamb skewers and las bombas. also try the mato con miel for a light natural dessert, along with the peach liquor.
Cafe paris- muntaner con paris, nice bar with excellent sandwiches. try the "paris" which is a triple decker ham, bacon, fried egg, lettuce, tomato sandwich. A good place to watch team Barca play. but has terrible service as does almost every restaurant in the city.
Lasty and excellent place for traditional catalan dinner with very reasonably priced entres considering the quality. La Clara on gran Via and Roquefort. The solomillo with a wine sauce and carmelized onions is amazing but make sure you make it clear you want it cooked poco hecho so they dont burn it because they think you are a tourist. also try the Calcots whcih are fried spring onions with a romesco sauce, or the fois gras with frid egg and mil hojas pastry. This place also has an excellent cellar of spanish wines.