IMHO, even if you're going to just pedal along nice woodland trails, I wouldn't buy one from Wal-Mart. The reason is the same as anything else you buy from Wal-Mart - they cut corners.
I've heard of plenty of stories where people would buy a bike from Wal-Mart, and then have a wheel bust, or a chain bust, or the brakes would fail, etc. Yes, this stuff could be upgraded, but you'd actually be better off to purchase a cheaper version of a better bike.
F'rinstance, if you buy a 'good' bike from Wal-Mart, it'll run you $150 or so, but it'll still be on the cheap. E.g., Mongoose. They used to be a great brand - as did Schwinn - until Wal-Mart got them.
When I got into mountain biking, I purchased a Specialized Hardrock A1 Comp FS, back in like 2002. It's a 'hardtail' (no shocks in back) with a front shock fork.
I enjoyed it because you could use it on some pretty decent trails - e.g., wooded trails, some small jumps (less than 7' or 8' jumps - meaning vertical drops), and the like. It wasn't the most fun to ride on the street - I wouldn't use it for a 10 or 20 mile bike ride - but then again, that's not what mountain bikes are for.
Anyways, that's what I did, and I haven't regretted it. Spending that extra $150 or so (I think I paid $400) got me vastly better shifters, brakes, spoked wheels, etc.
Actually.....now that I think of it, my father in law is HUGE into selling bikes. I was at their house for Christmas, and he literally has like 30 bikes. I distinctly remember seeing some mountain bikes there.
If you want, I can get information on which ones he has, and send it along to you with pics as well, and see if any of it interests you. He'd have to ship it - he lives in Virginia - but trust me when I say that the man treats bikes like a car nut treats a first-year Corvette. Let me know if that's something you're interested in...you'd probably save a decent amount.
