We liked La Vila de Gracia. It was quiet with bustling squares and pedestrian friendly passages. Casa Vicens and Parc Güell are easy walking distance.
Other attractions are easily reached by the efficient Metro.
Camp Nou, La Rambla, Boqueira, the beach, the train to Montserrat, etc. can all be reached by Metro.
The apartment is comfortable. It is 4 flights of stairs. It is quiet and clean.
Isabella is knowledgeable and helpful, but not intrusive.