As mentioned, there are many bus routes, and those routes can change throughout the day based on crowd patterns. If they have enough to fill up an entire bus for one hotel, they'll do it.
But there are a few general guidelines to how the buses are grouped:
-Resorts are grouped by geographical "zone". A bus will make a maximum of 4 stops if all stops are within the same zone. If they have stops across two zones, they'll have a maximum of 3 stops.
-A bus driver has free reign to visit their stops in whatever order they wish. Most stop at the resort closest to the airport, but some drive to the farthest one and then make their way back. Some base their route on stopping at the hotel with the most Guests first.
Even then, there are two exceptions:
-If the bus has passengers for the Grand Floridian, it will go to the Grand Floridian first.
-But if the Grand Floridian also has Polynesian guests, it will stop at the Poly first to eliminate a tricky left turn into the Poly for the driver trying to come back from the GF.
I've run the gamut of experiences: Had an AKL only bus (though it made stops at both Kidani and Jambo), twice have been the second stop as Pop Century after stopping at Caribbean Beach, and was the 4th stop at Riverside after stopping at Saratoga, OKW and French Quarter.
-Rob