Since you are just starting out and your commute is only 2 miles, I'd say to start off with a cheap used bike. Get a friend who knows about bicycling to help you pick out something off craigslist and go with you to pick it up. After some time, you'll get to know more about biking first-hand, and can then knowledgeably upgrade to something better.

Or if money's not a big issue, you could go straight to an LBS but make sure its a shop recommended by a fellow commuter. LBS's can be hit or miss. Without knowing much about bicycling, I went to get my first bike at an LBS who promptly sold me a bike that was way too small, too expensive, and not comfortable in retrospect.