Barcelona is very small, the metro reaches everywhere in minutes. Hence for lower costs, you can stay at the "edge" of town but still can reach town in minutes if you are near subway. I stayed at Vincci Maritimo near subway station Selva del Mar.
This is sort of near the beach... there are many chinese restaurants nearby if you are someone who cannot survive without Chinese food like me. The restaurants are operated by China people who migrated there almost 20 to 30 years ago, they are very nice and decent, they have been totally unChinified. Also a numbers of groceries stall operated by China people whom are again, unChinified.