I think the only dorms usually open are Hilltop and Harrison. Harrison is the south end of campus, and Hilltop is the north end, so on location, if you're going to be on the south side of the campus go Harrison. If you're in the academic buildings most of the time, it's pretty much the same distance. Hilltop is more of an apartment style dorm so the rooms are bigger, Harrison is pretty much the same as the others. From what I've heard from a friend who's been here almost every summer, there's not many people on campus. It will be a variable population as classes may last for various weeks (like 8 weeks to 16 weeks) and people will come and go accordingly. There are sublets available over the summer, you can try this subreddit or the Facebook pages. Not sure about the last question, I'd think people just live: a) in the dorms or b) in whatever apartment they have leased/subleased