We also rent in advance and this way are guaranteed a vehicle. I usually take an evening and go through all the rental agencies on this site to compare prices...the cheapest wins !!
BTW...have had the best service with courtesy, but haven't had any trouble with, Amigo, american or aruba royal...all have been good and the few times I had car problems all immediately gave me a new vehicle or fixed the problem...good luck.
I rented before hand, from Aruba Royal. No problems, he sent me all my e-mails with confirmation. When i got to the airport they were waiting for me. Brought me to the office, which is 2 minutes a way and 10 minutes I was off and away. I got a Toyota yaris for $337.00 for 2 weeks. I'm bringing back on saturday and they will drop me off at the airport.