I'm 5'1" and I commute on a Dahon. Nice thing about the folding geometry is that standover height is a non-issue for those with short legs. They're highly adjustable, too.

Bike theft is pretty high on American campuses - don't know if your University has a similar issue. Nice thing about a folding bike is you may be able to bring it inside with you, if you can find a space to stash it. I'm making a slipcover and strap carrying system for mine, so that I can bring it into offices that I visit, without worrying about getting grease all over things.

A mixte might work, too, if you can find one. Have you checked out the mixte thread recently?