If you get one, it should be the one with NO SUSPENSION, (there is a roadmaster with a solid fork for $100). The one I saw also only has one front chainring, so that's a plus (it has gears in the back). Check the brakes and gears when you get it, and lookup on youtube how to adjust them.

It will be fine for riding a few miles around town. Getting someone with knowledge to tune it up will help.

I rode a $200 wal-mart bike (Schwinn Varstity 1200) for almost 2 years of commuting (5-7 miles each way), and about 3 months on club group rides with the roadies before buying a real road bike. It worked well, but I had to replace the rear wheel's cassette and get it tuned up before it really functioned well. I was able to stay with a 20mph paceline, and climb some 5-6% 3 mile hills...but the road bike is obviously faster and better in every way...but I had fun on the walmart bike.

I sold it to a friend for $100, and he is still riding it regularly.