Nearest Social Security office to Mojacar Playa?

Hi, I've been reading other healthcare posts regarding presenting your S1 to get a number(?) or document to take to register at the local health centre, but could anyone tell me if there is a more local Social Security office than Huercal Overa?  I have moved to Mojacar Playa - without a car at the moment, and am hoping there is a more local office?  All help gratefully received, as ever,

Thanks, Polly S