UCSB, yep where my niece went as well. Isla Vista is a wild place to live. Definitely get a crappy bike, don't waste your money on a nice bike. The ocean air will also cause a lot of rust and be hard on the bike so go crappy and you'll be glad you did. The main 2 things to do to keep that bike alive for 4 years is keep the chain oiled and the tires pumped up (low pressure stresses the tires and cause them to fail prematurely) and you'll generally have no problems. It's all flat around there so stick with a single speed, a multi-speed that generally comes with hand brakes will just complicate things and is something for the ocean air to attack and cause maintenance problems that require constant adjustments. Like another commenter said, if the seat is quick release either lock it with a cable lock or take it with you.
A quick note on the lock, it'll not make sense on the surface to buy a bike for say $40-50 bucks and spend $40 on a good U-lock, but if it's stolen you're without a bike until you can get a new one so spend the money and have some peace of mind and not have the hassle of shopping for another bike.
Good luck in your education woodybr.