(I just got this from email) and it sounds like a really bad idea to send emails (or any kind of promotion) when there is no way to take an actual action on the website yet.
Since conference is quite soon anyway I thought it would be a better move to just open the registration and then do the promotion, but hey I'm sure you guys got something in your mind like defining the price based on interest, or something like that.
Oh, and we're not defining the price based on interest; the price is pretty much set (see my comment on this thread about price).