There is an lj community set up for this purpose, so you can join that as well to keep in on all the planning efforts.
We don't have any sort of official count yet as to how many people are coming and how many are staying, however as of the time I wrote this there were 17 members of the community. At the moment I'm planning for a group of around 20-25 people for the "main events", so to speak.
There are plans for a website on which everyone intent on going will sign up and state their intentions. Some people are going to be there only for one day, some for only the weekend, some for an extended stay. Because we have people coming from all over the world at the moment the major plans are for the weekend of June 5th and June 6th only, meetup-wise. Those would be the walking tour of Les Mis locations in the city on one day, a trip to Carnavalet the other day, meeting at Café Procope for absinthe one/both days, and of course the show.
We'll be digging about for ways to get discounted tickets and hotel accommodations and airfare for the less-financially-endowed of us. Trust me, if I have my way, this whole meetup affair is not going to go unplanned for too long, so there will definitely be time and discussion on all aspects of how to get there.