The interviews are generally very laid back-- I think they just want to get an idea of whether you are the way you've represented yourself in your application and to get a feel for your communication skills.
Funny you should ask this because I personally don't have a car (or a license. I'm working on it). There are a few of us without cars and we manage, but it's a lot harder. I'm from the city and I think it made the transition to the suburbs a little more difficult. Having said that, it's very easy to find an off-campus housing that's within biking distance and the odds are very high that you will have a roommate with a car that you can just split costs and carpool with. There's also an on-campus shuttle that works well for me because my house is right off of campus. Most people live in Stony Brook, Centereach, one of the Setauket's or Port Jeff, but there are a few other options.
But yeah, it's much easier and nicer to have a car. It's very much the suburbs here.