I know this isn't the question you asked, but what all is "falling apart" on the Wal-Mart bike? Learning to fix those things would build valuable skills, and a heavy-ish mountain bike provides a lot more of a workout than a zippy road bike. (For that reason, I've considered switching back to my roommate's 36lb Schwinn for commuting.)
If nothing else, this would allow you to save up your "bike money" while you do more research on BF.
- Scott