When I reached Orlando last night, I had no checked in luggage. Called the Parking when I got down from the train, so that they could send the driver while I walked to their spot. I stood for half an hour standing outside the airport last night. Every other parking spot had their shuttles come in twice (at least, one came in three times) during that period. The driver said that it was a very busy evening. There were just two of us in the entire van! There was no other customer at the counter. And then, after having given the ticket number in advance when I had called from the airport, had to wait while the car keys were being hunted out from the back. Any other parking location would keep the keys out so that the customer could walk away immediately with the keys. And I had prepaid for the entire parking period.
The trip to the airport from Signature Parking a few days earlier took an enormous amount of time too, since the ONLY shuttle had left just before I reached the counter after parking my car. This was around 4:30 or so in the afternoon, when you can expect lots of customers. All the while when they KNEW that I had gone to park my car after pre-paying for the entire period.
So, unless you are willing to keep 45 minutes or longer for EITHER way just to get to and from parking, look elsewhere.