It was very pleasant to meet David and to have some advices when you ask him about what to visit ...
The apartment was well situated in order to go to the Sagrada Familia (15 mn) and Park Guell, by walking .
You could take the metro or the bus and ask David for private parking of your car (if you need).
The bus 55 is easy to take for you if you plan to go to Montjuic (for one Day, many things to do and a great panorama of the town) and it's cheaper than to take Metro and funicular, to visit "Castell de Montjuic", "Fundacio Miro" ....
In Three full days, it's quite pleasant to visit the most important place in Barcelona.
We enjoy from Toulouse coming and visiting Barcelona.