There are not many B&B in Barcelona close to the best areas of Barcelona so you did well to find this one. Just a point to note that the B&B is just 15 minutes walking from the centre.. as you mention there is a metro stop close by so there is good transportation and the ride into the beach is only 10 mins by metro. The beach you mention infront the sea fod place is the Playa del Bogatell and Icaria beaches which are beautiful beaches with great restaurants for lunch or dinner.