Use of other Walt Disney World® Resort Hotel Pools
Disney Vacation Club Members and their guests staying with them at Disney's Old Key West Resort, Disney's BoardWalk Villas and The Villas at Disney's Wilderness Lodge are permitted to use other Walt Disney World® Resort and Disney Vacation Club resort hotel pools (other than the hotel at which you are staying) if these pools are not at capacity on any given day. A Walt Disney World® Resort ID card identifying you as a "
DVC Member" is required to use the other pools. This offer is not available at Disney's Animal Kingdom Lodge. Please check with the front desk of the destination hotel regarding pool availability.
Hotel pools may become unavailable from time to time due to capacity limitations. Due to the high occupancy that is expected over the long holiday weekend (June 29-July 5, 2001*), Disney Vacation Club Members may not "pool hop" during those dates. If you are using the pool at a resort other than the one where you are staying, you may be asked to leave in order to accommodate guests of that resort.
*Other restricted dates may be added based on projected pool capacity.
Here's the whole write-up. It pretty much lays out the procedure for pool hopping and lets you know that you probably won't be able to use a pool over the July 4th holiday. They do leave that loophole about being prepared to be asked to leave.
Pool hopping at NYE depends on the weather. When it's in the 40's most of the pools aren't all that full.

If you hit summerlike weather then the pools may be filled to capacity then as well.
If the announcement of another large DVC resort is true, then pool hopping will probably be further curtailed. The pools can only absorb so many additional users.