Yes and no.
I will say that they aren't going to be as good as your car seat (depending on the kid). We took our 6mo. old daughter to WDW in November, and at the last minute decided to take our car seat. We had booked with
FL Tours and they did have a car seat waiting for us, but it was very loose & looked more than a couple of years old. For an infant, I'd take our seat again. For an older child, it would probably be fine.
Sarangel