I developed PF about a year ago. A couple of low-budget alternatives to the Sketchers & FitFlops are TheraShoes (and TheraSandals, made by TheraShoe) and the RocknFit rocker shoes. I found both at K-Mart but am sure you can get them other places too. The TheraSandals are like flipflops, while the other two come in a variety of sneaker styles. All have high internal arch supports and the rocker bar/heels. Wonderfully comfortable for all-day walking.
Other than that, dose up your anti-inflammatories a few days before you go to Disney, make sure you do your stretching (a few good stretches before I get out of bed in the morning eliminates the massive pain I used to get on those first few steps), and see your doctor if the symptoms worsen.