Flat tires are extremely easy to fix. Even if you take it to the store, it's only about $5 (unless you buggered up the rim, then you're looking at ~$25, and you can't do it yourself).
I really buggered my bike up the other day. I split the tube into two peices, tore the tire so the tube stuck out if it was pumped up it'd pop again. Had to buy a new tube and tire.
And that cost what? $5?
The less I can ride my bike the more I'm pushed to learn how to drive, so I have no intention of doing anything to fix it any time soon.
Biking > driving. It's WAY cheaper, more healthy, better for the environment, and you get a strange respect from people when you do a long commute (25km each way, in my case).
Of course, you ought to learn how to drive and get a license. But beyond that, I prefer biking.