I use my road bike. It's not anything fancy (a 2005 Giant OCR1). I'm lucky that I can take it in my classroom and not have to leave it locked outside all alone. I'd be nervous taking a brand new bike and leaving it locked outside all day. Maybe you could snag an old steel frame or older aluminum bike on craigslist or eBay and use that as your commuter.
BUT... this advice is coming from someone who doesn't trust people to not mess with my things. I'm protective of my toys.