Well, checkout time is 10:00 (a small rush) so I would plan for some time after that. I don't think I would arrive before check out time. We usually arrive around noon because of flight times and have pretty good luck getting into our unit(s).
Well, no guarantees since the mix of guests changes regularly. But this is a timeshare resort, so the majority of guests are owners. The young adults age range is usually underrepresented as a result - most owners are well established in life. I rarely hear bad language, or witness poor behavior, but perhaps I'm just lucky (or deaf and blind

).
I don't have the resort map handy, and searched around a bit trying to find my post with the actual building numbers. It's on here somewhere. If you are staying in a 1BR, you needn't worry as the units in question are in Fountains (1BR's only in Cascades/Lakes). The I-4 backing is at the very North edge of the property; at the top of the map they give you when checking in (and they don't show you where I-4 is on the map). One way to avoid these buildings is to insist on a water view. These are the only units in the Fountains section to not have a pond or pool view.
Hope that helps and you get your Happy Ever After...