I agree with Kate, people use to complain in summer about no car rental avaibility. If you know you will rent a car in Malaga for your holidays, my recommendation is to do this ahead of time. Malaga is a very popular destination and in summer a lot of tourist come to enjoy the weather and the beach. If all the people want to rent a car in the last minute, is possible that companies run out of cars, but if people make the online car rental reservation a few months before coming, the car rental companies will expand their fleet of cars when needed.
Remember, you are coming to a popular destination in Spain, make your planning and reservations with time
Malaga holidays resources:
Car hire at Malaga airport
: Many websites where renting a car in Malaga and at Malaga airport without credit card, just using a flight number.
Malaga airport transfers
: Malaga airport transfers, if you are planning to come and need a private taxi for getting to your hotel we have reviewed here the best airport transfers websites.
I think those resources listed above will help in making your reservation ahead of time without problems.