From the DVC Member Website:
Pool Hopping Information for 2007
You and any Guests staying with you at Disney's Old Key West Resort, Disney's BoardWalk Villas, The Villas at Disney's Wilderness Lodge, Disney's Beach Club Villas or Disney's Saratoga Springs Resort & Spa are permitted to use other Disney Vacation Club and Walt Disney World Resort hotel pools (in addition to the pool at the Resort hotel at which you're staying) if they are not at capacity.
If the pool you are visiting reaches capacity, you may be asked to leave in order to accommodate Guests of that Resort hotel. Please check with a Host/Hostess at the Front Desk of the Resort hotel you wish to visit to find out about pool-access availability. You must present your current "Key to the World" card with your Disney Vacation Club "Member" designation on it to use other Resort hotel pools. Pool hopping is not available at Uzima Pool at Disney's Animal Kingdom Lodge and Stormalong Bay at Disney's Yacht & Beach Club Resorts or at the leisure pools of these two Resort hotels. There are no exceptions to this policy.
Resort hotel pools may become unavailable from time to time because of capacity limitations. Due to expected high occupancy, Disney Vacation Club Members may not "pool hop" during the following dates*:
February 18 - 24, 2007
March 31 - April 8, 2007
May 25 - 28, 2007
June 30 - July 7, 2007
August 31 - September 3, 2007
November 19 - 25, 2007
December 16, 2007 - January 2, 2008
*Other restricted dates may be added based on projected pool capacity.