Below is a list of locations where you can find actors to cast for your films:
http://www.solocastings.es/castings-en/barcelona/
http://es.yatecasting.com/castings/1/barcelona
http://clandestinodeactores.com/index.php/castings
http://www.casting.es/castings/los-castings.html
http://www.modelmanagement.com
Finding English Actors can be a larger challenges. Below is a list of theater companies and other groups of English speaking actors to get in contact with English speaking actors:
http://www.freewebs.com/actorsworkshop/
http://www.joculartheatre.com/
http://www.englishtheatrecompany.com/
http://www.barcelonaimprovgroup.com/