Hear this out loudPauseNo shorts. You don't have to worry about dressing too skimpy or revealing, however, it will bring you extra attention (if that's what you want). Many, if not most, of the tourists walking around Barcelona were scantily clad and looked plain ugly compared with the conservatively and elegantly clad Spaniards.
What clothes to travel to Spain?
Hear this out loudPauseYou're therefore going to want to pack lots of lightweight, cotton outfits that'll keep you cool in the heat. Two strap tops: Spain is hot as hell, so you're going to want to wear lightweight, thin tops to stay as cool as possible.
Do people dress up for dinner in Spain?
Hear this out loudPauseIn the evening, local women dress more stylishly, particularly when dining out. If you are going to an average to high quality restaurant, you'll be more comfortable wearing something more dressy. Our advice would be to save your shorts and sarong for the beach; wearing them elsewhere will label you as a tourist.