I have lived on the south coast of Spain for 8 years now, and to be honest the fishing is not that good. There are local waters where you can have good sport, try out new tactics etc but the real fishing is inland, Cordoba and beyond...
Most of the lakes here have stories of big fish (20+) been caught, however the problem is that neither the Spanish or our Eastern European friends practise capture and release and many of these fish have simply disappeared. This coupled with the drought 8-9 years ago, a lot of places dried up and the fish died. Unfortunately there is no restocking program or proper fishery management here so it is open to severe abuse, only yesterday we visited one of the lakes near Puerto Banus and it had 20 plus pop bottles floating around with line, hook and baits attached. A friend called the Guardia Civil and they were not interested...
Remember to be legal, you must have a license and insurance, do not listen to people that say you do not need it, having been stopped by a 5 car ambush of police and the Dept. Medio Ambiente I can assure you that you do need them, and remember its a maximum of 2 rods and no night fishing!
Enjoy your sport down here, but if you want real big fish hunting head North, it's a big country!