Better info:
Open enrollment (or it is now called Individual Enrollment) is only available periodically.
It is presently available (in August and September) and it looks like it will be available in January
Here is a better link that takes you to the Individual Enrollment Page:
http://www.disneynow.com/profile/form/index.cfm?PKformID=0x24302f743
To see what is offered, click on the “Order Tickets Online Now” button. Then fill in the fields with some fake information and click ‘Continue’. Fill in some dates that you might be interested in, and click ‘Continue’. Pick a ticket package that interests you (prices are valid for both adults and children, prices are about 50% off for adults) then click ‘Continue’. Then it shows what classes are offered on certain days.
For a good discussion of the program, go to:
http://www.disboards.com/showthread.php?t=2332767&page=55
For example: A 5-day adult Premium park hopper ticket (5 days in the parks and 5 days at the water parks) would cost you $367.43, if you bought your tickets through the usual way. Under the YES program, it’ll cost you $173.68.
I’ll have to bear that in mind for future years. The eldest is just starting kindergarten (the YES program is 1st - 12th grades) and the twins are in special education preschool.