People with head injuries can remember what they were able to do before the crash, and the effects can last forever. At your age you have a lot of years to look forward to. You are just beginning to realize how much pleasure in life comes from being smart and educated. You don't want to take a chance with that. It means a lot to you.
Helmets are cheap, and the cheap ones work fine.
You can lock it with your bike. It won't mess up your hair much in a short ride. Give it a try. Check out our Campus Bikeing Tips 101 Suggested by Brad Russo, a student at Dartmouth. May 1, 2001.