Don't really have any breakfast recommendations, mostly a cappuccino and small pastry are what most eat.
Since you are near Placa de Catalunya, I will give you several restaurants near that area that my friends in Barcelona and I enjoy.
For real Catalonia food try La Lluna, carrer de Santa Anna, 20 - it is actually at the end of a side street carrer Sant Bonaventura - you will see the menu board on Santa Anna. It has the traditional monk fish, cuttle fish, octopus, squid, etc. They have a set lunch menu at 12.95 for starter, main course and dessert. Open on weekends for dinner. Lunch on weekdays.
For tapas, tapes - Tosca del Carme, Carrer del Carme, 40 is a great choice.
Barcelona has good international food as well. Try Torres del Paine, Carrer junta de comerc, 28 - this is a Chilean restaurant.
El Pachuco, Carrer de Sant Pau, 110 - a Mexican Restaurant.
Rajah Restaurant, Carrer Nou de la Rambla, 3 - this is a Pakistani Restaurant, they have a great set lunch menu on Mon -Thurs. for 12.95
There is also a great buffet restaurant that a lot of locals go to called Fresco. It has a main local dish plus pasta and pizza for the kids or adults, along with a never ending salad and dessert bar. All for 12.95 near the Placa de Catalunya or 13.95 near the marina.
Hope this helps.