This is the most popular beach in Barcelona though there are far better Beaches in Barcelona
It scores ten out of ten for location (less than ten minutes walk from Metro Barceloneta) and is well equipped with restaurants and bars, but the sand is truly awful. It is an artificial beach and I have been reliably informed that the sand is a mixture of real sand and concrete. Makes the idea of sunbathing there a little less pleasant!
But if you're looking for a cheap beach vacation in Europe, you'd be hard pushed to beat this. For about twenty euros a night you can stay in a youth hostel (Equity Point Sea) right on the seafront. Book this hostel at Hostelworld.
Barceloneta beach is in my Free Things to Do in Barcelona.