I always would start trolling car rental sites even before I had a reservation, as long as I had an idea of when we'd be traveling. Prices go up and down all the time, just like the airlines. If your trip is during a holiday such as Spring Break, Thanksgiving....any time school is out, finding a bargain will be difficult. Sign up on the rental car sites for their rewards programs, it helps. If you see a price you can live with, book it but don't pay for it up front because then you can't cancel. If you find something cheaper later on, you can cancel and then get the better deal. Just read the fine print. Always pick up and return your car to the same place. Just know that renting directly within MCO is more expensive then if you rented off MCO property.