Back when I had this same decision I actually bought the computer before I bought a car. Public transportation (e.g. bus) is not always fun but it gets the job done. I don't regret the decision, although not having a car may not help the social life it definitely helped me learn a lot about computers, especially when you're stuck at home because you can't go anywhere because you don't have car.
Learning everything I did from computers helped me not only get jobs but also a lot of good paying jobs and high positions because of my skills. Sure a car may make it easier to drive to a job, but if you're looking for a job in the computer industry someone isn't going to hire you just because you have a car they're going to hire you because you've got the necessary knowledge to get the job done.
All that being said thankfully now computers are pretty cheap and if push comes to shove you could easily just get a cheap few hundred dollar computer and save the money for a car. My first computer was several thousand dollars, which today isn't really necessary for your first computer, especially if you're needing to make the decision between a computer and a car. In fact buying a cheap computer may be even better if you plan on fixing it up and/or want to learn *nix (Linux).
