Honestly, it sounds like it's going to be hard for you to make that call if you don't have much bike knowledge. What you can do though is search somewhere like craigslist for bikes in your size, then come back here and post the info. I'm sure you'll get plenty of opinions about it's quality and value.

In that range, you really have two options. The first is older road bikes. The other, and perhaps easier to find, would be a mountain bike (preferably without suspension). Replace the knobby tires with something smooth and you're set.

If you look at this thread - http://bikeforums.net/showthread.php?t=49471&page=107 - you'll see that people here commute on just about every kind of bike. (I've linked to the last page because you'll see more pictures if you start there and move backwards - most of the early pictures are broken links now).