My suggestion would be to get something off of craigslist. You would have an opportunity to test ride the bike to see if it fits and look over the bike before you buy. I would look for a name brand bike that is maybe a few years old to save money.

There may also be a LBS that has a used section (you may need to ask an employee since it might not be on the showroom floor) or a bike co-op in your area.