We just got back with our 20 month old. I took a cheap umbrella stroller with a hood, because I knew I would need something light to get on and off the bus by myself with my son. I figured DH and I would be separated some, so he could stay in the park with DD8 and I could take my son back to the room for naps. DH is big on riding the buses everywhere, hates to drive once we get there, though we do have a car, because we drive down. I did pack my nice P3, though, since we would be driving to Sea World one day, and I could use my nice stroller that day.
Well, we never did make it back to the room for a nap, because ds fell asleep in his stroller each day. The umbrella stroller didn't recline, so his head was all slumped, and I ended up just sitting beside the stroller holding it a reclined position for the duration of the nap. Not fun. So, after two days of that cheap little stroller, I told DH he could ride the bus if he wanted to, but DS and I were driving so I could use my nice stroller. Driving worked better for us, and the P3 was so nice-comfy, easy to push, full sun hood, full recline, tons of storage, not tippy when you hang stuff on the handles. Just giving you my 2 cents, because I read in several different forums that its best to take your "better" stroller to WDW, but I must have been in denial. But they were right, this may not be the time to experiement with a cheap umbrella.
Either way, have fun! I wish we were leaving again in 2 weeks!