In reply to lady_radiation:
The best crag for grade spread, position and route quality is Gelida, about 40 mins drive from the city centre (you need a car).
The Rockfax guide does a good job of getting you there but, beyond that, is a bit useless now (sorry Chris), as more lines have been added since its publication. If you google 'Gelida ressenyes' you should be able to find some more up to date topos.
Of the other crags in the rockfax guide (I've climbed almost every route in it), both Pas de la Mala Dona and Penya Ginesta are worth a visit, all the others are best described as 'for local interest only'.
Montserrat is about an hour from Barcelona, and is a different experience altogether.