The best way to connect yourself to the internet in Barcelona with your wifi-able laptop is to become a member of the public libraries of Barcelona. Almost every one has a wireless router which you can access with your member number. It is totally free and the buildings are amazing, they give you a map and information about opening hours when becoming a member.
Right now I am sitting in the one in Raval, the Biblioteca Pública Sant Pau – Santa Creu in c/ Hospital. It is 15min before closing and they have the nice habit to turn on some music. In my case it’s Boby Dylan’s “Everybody must get stoned”.. Pleasent places, really.