I would find a cheap older road bike on Craigslist. I commute on a 1989 Bianchi Brava. It only cost me $100 and after fixing it up, it runs really well. I would be sad if it got stolen, but not as bad as if my race bike was stolen. You may also want to look at hybrid bikes with flat bars. They usually allow for more clearance than road bikes and have places for fenders and racks if you decide to really get into commuting... My commute is only 4 miles so I just use my road bike with 700x28c tires and wear a messenger bag.