I cant acount for the situation in the Costa Del Sol but I would imagine it wont be very different to elsewhere in Spain. Jobs within bars and restaurants are going to be hard to find, with many people competing for any work (including part time, irregular hours with little / no contract with the employer) in this particular arena.
It seems that many Restauranters and Bar owners are struggling (rising costs and reducing demand) and are not keen to commit to a contractual arrangement with their staff. Restaurants and Bars are closing all over the place, although its probably fair to say that reducing competition in some areas means that those that are able to remain open are possibly remaining afloat in this stormy economic environment.
There will probably be summer work in the CDS, but like I said ....the competition is going to be high.
Good luck whatever you decide to do