From what I've heard the boats do not run between all three hotels, so to get from PBH to RPR you'll have to wait for the boat at PBH, go to CityWalk, then wait for the boat from CityWalk to RPR. It may not be bad, but if there's a line for the boat at CityWalk or you just miss the boat and have to wait, it could take a while.
You could also just walk from CityWalk once you get there if the wait may be a while.