In reply to CrystalG:
Montserrat (conglomerate), La Mola de Sant llorenç (conglomerate), and Garraf (polished limestone) are closest to Barcelona.
The topos for la Mola:
http://www.santllors.com/sector.php?id=209&zona=1
You will find topos for a variety of sectors in that link, Font soleia concentrates most sport routes, some in the shade, routes seem hard for the grade, graded by locals.
I would stick to the shade if you are coming in these hot months.
In Garraf beware off car thieves and the approaches can be difficult to find.
If you have time go further afield I recommend it, go to Montral which is in the sierra de Prades, closer to Tarragona than Barcelona, great hut there and good but cold swimming spot near the river sector.
Then there is Margalef , Siurana etc, all in the Tarragona climbs guide book.
Loads of places, too many.
Have fun
Post edited at 22:52