I always park my rent-a-car in the carpark downstairs (where you would deliver your car after your stay) and leave a note in the window saying I'll be there for a short time. I even do that when I do short trips to London/Oslo and am away for a couple of days. Never had any problem with that, and it is absolutely no charge to worry about.....
Done it for many years.....
A simple and easy solution whenever I pick up my guests too.....
Follow the sign "Llegadas" (arrivals) as you arrive in the airport and drive past the taxi-rank. On the left hand side just after the last red zebrastripes you'll find the entry into the parking.
Lanza airport is unique in many ways, - this is one of the real benefits you have.......
Cheers......