For something that's going to be a quick turnaround I'd suggest that you look into hotwire.com or priceline.com. Though you should be cautious with your bidding - I always suggest that a bidder/buyer never go below a three-star level with either of these online companies.
For Priceline (name your own price), I'd suggest focusing a bid on the Universal Orlando Resort Area-International Drive North area if you think you're first day will be at Universal Studios or on the SeaWorld-International Drive-Convention Center area if you go to SeaWorld on that first day. You ought to be able to find a three-star or better hotel room for $50 or less.
For Hotwire, a few three-stars should pop up at $50 or less.
Dick Taylor