I usually go to l'Escala and dive at Montgo' Sub. It is run by Quim Pallas. Tel 011 34 972 25 52 69 (from the US) He is very layed back and probably wouldn't look too close.
Also, very near is l'Estartit, a national park. (Both are less than two hours (150 km) out of Barcelona. (North) L'Estartit is a little touristy.
More info can be seen at
Scuba Diving around Cap Creus and the Bay of Roses, Costa Brava Spain
Dale