If you have any friends who are into cycling and would be willing to help you find a good used bike that might be best considering your budget. You should be able to get a quality used bike for a couple hundred bucks. If you want a road bike you can often find good ones from the 80's or 90's cheap enough that even if you need to take it to a bike shop to have them tune it up/overhaul it for you, you should still be able to come in under your budget and will have something much better than a department store bike. The trick is to do your research and find out which brands to look for, and to be able to recognize the difference between low end and quality bikes. There is a lot of info available on the internet. If you find a couple on craigslist or something you think might be good you can post links on bike forums and you might get some good insight.