Why do you need a suspension bike? If I were actually going to do mountain biking that requires full suspension, I certainly would NOT want to be on a walmart bike! Commuting and town riding do not require suspension, in fact, a suspension bike will just slow you down on the road.

Really, you should look at some decent used bikes. Machka has alot of experience and know-how to deal with her walmart bike, and it has worked for her. If you have not biked in a long time, do you really want the hassle of making a walmart bike work when you can have a better trek or specialized bike? Even used, those bikes are better quality, and if you get it from a bike shop, it'll likely be better assembled and you'll have real service.