My sister used a WalMart Mongoose bike to get to and from work. One day, the handlebars BROKE as she was riding up a steep hill. She fell into the street. Car swerved, she luckily wasn't hit, but had a huge bruise on her knee and couldn't work or anything for over a week.

I rode a WalMart Huffy wannabe road bike a few weeks this summer to and from. The brakes weren't brakes. They were "slowers." I didn't really realize this at first, and almost went careening into the path of cars. Emergency stops are impossible, and its was really annoying having to start braking 100+ feet before where I actually needed to stop at.

My biggest issue with WalMart bikes is safety.

I'd shoot for any of the lower-end of the name brands like Trek or Giant, just to name two. I see these these reputable brands ALL OVER THE PLACE on craigslist and such. Try thrift stores too, there are good finds to be had there.