Yes, you can always book at your home resort 11 months in advance. Think of your UY is when your points go from being next UY's points to current UY's points.
When you call to make a reservation, everything is based on the UY of travel. Any trip can be "paid" for using banked points from the UY prior to travel, the UY of travel, and borrowed points from the UY after travel.
So, if you have a June UY and want to travel in January 2013, it would take place in your 2012 UY. You could call to book this in Feb 2012. MS would then look at your account and use any banked 2011 points you have, 2012 points, and then borrow 2013 points if needed.
Traveling at the beginning of the UY gives you the most flexibility in terms of what you can do if you have to cancel, change, or re-schedule a trip, but plays absolutely no role in when you call to book your trip.
Hope this helps!