I think if you book a non-theme park view room it will be less of an issue. When we stay at CR, I do hear the boat horns, but they don't wake me. Mostly, I'm already up. Sound from our neighbors was more of an issue at Poly for us than the boats during our last stay there.
For that matter, the Water Parade happens sometimes as late as 10pm. For us, it is like our lullaby if we are in the room at that hour. If I was trying to sleep before it, that might wake me up, but agai- more if you are facing the water/theme park view.
I don't know if they all it standard view or garden at Poly, but that's what you'd want. I think you could also ask to be in a quieter room when making a request.