Most web sites offering airplane tickets will allow you to book a car in advance. Car rental is not expensive in Spain, but check that all insurance is included in the rental price.
A few rental sites are www.marbesol.es, www.malagacar.com, www.hellehollis.com and www.eautohuur.nl. Also, this comparison site finds you the car of your choice at the lowest rate.
If you intend to combine your stay in Los dos Algarrobos with a car trip through Andalusia, we recommend booking the car as part of the overall package.
The above car rental links are offered as a service - we do not accept any responsibility for any problems.