Carjet are fine, but as Malaga airport is under construction a lot of car rental companies are now based offsite.
Not sure when the airport will be fully up and running and if all car rental companies will return or not?
I didn't bother with going with Carjet earlier this year and went with Avis as they're based at the airport which made things so much easier as we arrived on a late flight.

Driving in Sothern Spain is relatively easy as thre are so many Brits out there!