The shortest answer is of course to keep a close watch on the website: kpjayi.org as things change and nothing is set in stone. There is a “News” section that keeps updating with information.
When I checked the website back in August’11 they had information pertaining to when Saraswathi and Sharath were to start teaching, or traveling, etc.
When to Register:
Early. The best idea is to check the website and see what is happening at the particular time.
I would start looking from March (or from when the shala closes) and on, because that way you can be on the lookout as soon as new info, for the next period of teaching, appears.
You will see announcements of Sharath and Saraswathi on tour (maybe you can make it to one of their international trips).
NOTE: The Shala says now that they only accept applications 2 to 4 months prior to your arrival. At that time you can send the online registration form.
One Way to Prepare:
In the meantime, consider that to register online you will need a scan of your passport, the page that has your name. While at it also scan the visa part, take four photocopies of both pages and take 4 passport pictures. You will need them for the trip.
When to Go:
No matter when you go, it will be crowded…
Sharath fills up much faster than Saraswati in my experience… So send your app early on, and plan ahead.