Ah this helps. There are still many speculations to the opening date. Many rumors flying around that it will be opening on Memorial Weekend. But the deadline for the park to be completed and open is June 30th. So it may or may not be open on the 19th. I know this doesn't help in your decision making.
To answer your original question, IMO yes it would be worth it to stay on-site at Universal. Looks like you would be arriving on a Saturday. If so, and if HP is open by then, than it might be safe to assume there are going to be very large crowds. This is just my early assumption.
Undercovertourist.com sells tickets at a better price. They usually have the best prices. I've looked recently and they are cheaper than buying them directly through Universal's site. Might be able to get a good room/package deal though. I would certainly look into that as well.
I'm sure Damo and Metro will be along soon. They seem to be the some of the Universal experts on here. They can give you a better take on things, better than I can. I don't get to go out to Orlando very often. So I hope there are others that can help answer your questions.
Hallway noise? neighbor noise? outside noise? I'm good with rockin' and cool! 
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