If this is your first visit, stick to BCN...there are amazing places to visit outside the city, but for a first time and with a limited amount of days, best to stick to discovering the city itself.  A few thoughts:   
 It is tourist season, so it will be crowded. Very LGBT friendly city, but the tourists can be total bigots 
Stroll thru Las Ramblas 
Save a day for the beach 
Must check out Parc Guell - the views are stunning.  
If you like live creatures, the aquarium is very modern and cool 
 
Enjoy & share back what marvels you discover - including the men!