You will find Hertz car hire in the Malaga airport car rental zone which is below the baggage retrieval level reached by walking down the ramp just before the exit into the arrivals meeting area.
Hertz have other offices up and down the Costa del Sol in Fuengirola, Malaga city, Marbella, Algeciras, Granada, Cadiz, Jerez and Seville. I have used Hertz out of their Marbella office a number of times when my Visa company would send me a promotional code for a very cheap weekend away with an extra day's rental thrown in for free. I would order a middle range car and ask politely for an upgrade which I sometimes got and sometimes not.
I enjoyed the extra power of the upper range Hertz rental cars for overtaking on the wide open road to Portugal, on the other side of Sevilla.
I used to use Hertz when hiring a car on my visits to the UK, now I do all my car hire through Cartrawler, see the link on this page. The deals are very competive world wide.
Hertz hire cars can be booked at Malaga airport. You will find telephone and email contact details for the Hertz Office at Malaga airport here.