Join Date: Jun 2004
Location: Northern Nevada
If you know a little about bikes, you might take a month or so to check thrift shops. I've scored a couple of good bikes for friends at places like the Salvation Army or Goodwill, usually for $50-$100. But you need to be able to evaluate them and usually do some work on them, and it's a bad time of year for used bikes--school will be starting soon, and people are buying bikes to take to college.
Just personal preference, but I don't like fixies, at least for inexperienced riders. To me, they're more trouble and risk than they're worth. I enjoy my singlespeed, but I built it from a good bike to begin with. Cheap ones are apt to be heavy, poorly built and indifferently assembled.
This is more a list of things NOT to do than a guide to finding a bike, but for the money you have (no reason to be embarrassed--most of us have been there), I really think you should shop around and try to find something used.