[QUOTE=Cavey;1105245]Definitely call. You don’t want your early arrival time turn into a long wait at the airport for your assigned bus.[/QUOTE]On your arrival day, when you land at MCO, there is no assigned bus. You get shown to your bus queue, and you simply get on the next one available.
As long as your flight NUMBER hasn’t changed, there is absolutely no reason to contact Disney’s Magical Express. Their computers are hooked into the airlines’ databases … if your flight changed times, they know it before you do.