It's never too late to join until Monday when I start the game and it will be too late to join.

Oh and you can all start making alliances now (via pms or you can go public if that's your game plan) and then start backstabbing when the game starts and voting begins.

You don't have to make alliances with anybody, but I doubt you'll get very far. You don't have to backstab anyone either, but where would be the fun in that?