Hi young bob...Hope I may be of some help. I´m approx four hours from Malaga, further up the coast near Mojacar. I passed my OW here last year. Costs can vary quite a bit. A spanish operator in Carbonares [ 26k away ] was charging 265 for Padi OW, English dive centres normally charge between 325 to 365 where I live.
If you haven´t dived before, you could try a " Discover Scuba Diving " pack, around 60 to 75. It´s one day, a little training, and then you do one shore dive. Most places will take this off the price of the Padi Open Water course, should you decide to go the whole way. Water temp in Jan was 14c, by May it should be approx 18c.
Hope this helps.
Dive Safe.