I like mr geeker's idea of the $100 Wal Mart bike, for you.

That bike will do just fine for a 6 mile commute.

And it's inexpensive enough that you don't have to worry about dropping it, or leaving it someplace where it could get stolen.

I rode a Wal Mart bike for years before I upgraded. I don't have to tell you that you'll get a much nicer bike if you spend more money.

But for what you need today, that $100 bike is probably fine.