If you're willing to spend $200, don't get a walmart bike. Almost any used quality bike will be far better. I'd try to find something new-ish, maybe made in the last ten years or so. This will probably get you front suspension (which I suggest.) You can find nice stuff for $200, just post it up here and ask if it's any good. Searching www.bikepedia.com for the bike you're looking at is great because it'll tell you all the specs, MSRP, etc. Good luck!

I know you're in Colorado, but for example, this one looks pretty good: http://madison.craigslist.org/bik/1980353794.html