I do believe it's too late to sign up, since we have started quite a while ago. Rep has a bit of hard time updating the site though, what with the area where he lives being bombed and all that. However, a lot of players are doing their duels against all the people in their league already without waiting for the next rounds to be announced.

If you're really lucky though, someone else will withdraw from the tournament and you might be able to take his/her place. It has happened a few times, though I guess it's up to Rep to decide.