Well, this is all really, really good food for thought. I appreciate everyone's input!

I think I may wait to get on campus and get a better feel for my commute and so on before making my decision. I suspect that I really can take the bike inside more than I'd thought, as everyone suggests. I also suspect that there will be times when I'll need and want to leave it outside, though. The general consensus seems to be this would be a Bad Thing, and it does make me nervous, so...

Maybe I should be looking at a used Dahon or Tikit. I may even try to figure out a way to make a beater work, but I think I'd lose too much mobility. I'll give it some thought. I don't suppose there are any Brompton covers or bags that allow it to continue rolling effectively? Am I right in thinking it's easiest to roll with the handle bars still up?