Everyone here is going to tell you that $300 is too low, but you're a college student so I'm going to assume you're living in a dorm and can't bring the bike inside. It'll be subject to weather and bike thieves. Therefore you don't want to spend more than is absolutely necessary. The minimum for a reliable department store bike is $150, but you should know that you'll need to make adjustments; most department store bike assemblers could care less if it's rideable, they just need it displayable. By going ultra-cheap, you'll learn basics on how to keep it going so when you get your own place with an option of indoor lockable storage, you can get a proper bike and know how to maintain it. Also, the ultra-cheap ones, if something serious breaks or is stolen, you can just chuck the whole thing and get another. And you're still ahead of the guy who went name-brand. Also, as an added bonus, bike thieves know the good brands so your Next will be left alone while everyone's Treks and Cannondales have crap stolen off them daily. *Any* bike is better than walking.

BTW: I've put anywhere from 800-4000 miles on various department store bikes so quality is a crap shoot. Look at the ratings online first. If it's rated low, AVOID. All my experience is with mountain-style bikes, and I wouldn't try a dept. store road bike at your size since the MTBs can barely handle full-sized people's weight and power output.