Do they sell S2 or even S1 at a store (GameStop, Wal-Mart, Target, ect.)? Or do you have to buy it from online?

It's only available online on lfs.net

Once you've upgraded your account (by buying the game online) you'll be able to unlock the game without any additional downloads (if you have the demo installed already )

Can we play with people who havent bought S2 yet online, and when is S3 coming out?

Yeah you can. If you download the demo you can play with other demoers.

And s3 wont be out for a few years yet.

Edit: if it'll ever come out, at the speed of development lol.

So if i buy S2, i can play with people who have S1? And also if i buy just S2, do i have to also buy S1 for those cars + track?

Quote from Buhnanah :

So if i buy S2, i can play with people who have S1? And also if i buy just S2, do i have to also buy S1 for those cars + track?

S2 is the full package of what is available. You can play with people who have S1 and even still play on demo servers (but why would you once you have S2 ).

Also, in case you haven't seen yet - the difference in content of S1 and S2: http://www.lfs.net/?page=contents

So when I buy S2, S1 is already included in the game?

Correct

Thanks