screw the $100 wally world bike. You kinda get what you pay for here. Not saying you need to go out and drop $2k on something but if you can put together a couple hundred you will get a much better bike.
Best thing to do is go waste some time at a bike shop and make sure you get the proper sized bike. The worst thing to do is get the wrong size cause you will hate every second of it. Most of the time the shop will help out with any adjustments for the first yr or so, dept stores lack any sort of service if its needed.
You dont really need to stick with the major name brands. There are plenty of other companys out there with great products. The good side to the name brands is generally a little cheaper. I'd suggest getting a mountain bike and then you can use if for anything.
usually there are people selling parts and everything here:
http://www.morcmtb.org/forums/forumdisplay.php?f=18
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