Thanks, everyone, for all of the advice!

I am terribly excited to get into cycling after reading this thread (and many others, too!) I decided to go with the Carema Pro. It is in immaculate condition, and although it is REI brand, it is a step above entry level and it was under $400. I imagine I will continue being primarily a runner through college, but this bike will be a good introduction to the sport/cross trainer. Maybe when I have a real job after graduation I can look for something a little bit nicer (although things like rent, a car, food, utilities, etc. might get in the way of that ).

Again, thanks for all of your help.