When I was a poor college student I had one bike for everything - transportation, recreation, fitness and touring. I'd suggest you look at bikes that will accept a rear rack (i.e., no carbon seat stays unless they specifically have rack bosses) and might have a more comfort-oriented geometry than a full-on race bike. Not going too expensive is actually a bonus on a transportation bike, since it'll be less attractive to thieves.
But yeah - try out different bikes, see what you like, what fits, what speaks to you. Good luck and enjoy the search (and welcome to TE)!
Speed comes from what you put behind you. - Judi Ketteler