If you are driving down and are looking for a cheap place to stay, there are plenty of places to stay right outside of Disney. I have stayed at a couple of choice hotels (comfort inn/suites) and found the internet rate to be reasonable. Just do a search on the choice hotel web site. They also have refridgerators, so you can cool down some stuff. They weill have a free continental breakfast. La Quinta Inns are also generally inexpensive and have continental breakfast, This works well if you want to hit a grocery store when you arrive, crash for the night, and check in early the next am at POP.
You could also try Priceline or hotwire for an inexpensive place, except you won't know what you are getting until after you bid/pay.
If you are using Disney transportation then I would add one night room only to the POP reservation.
I know there are walmarts and a Target on the way to the airport, but I couldn't tell you how to get there.