I believe the timeframe is actually 5-7 days prior to check-in for the reservation information to be transferred from the main computer to the resort's computer -- at that point, the room assigner will see the record and will be making tentative assignments for the rooms. If you get your fax there and note your check-in date and reservation number on the fax, it will help them understand your wishes and do their best to give you what you request.
By the way, the fax numbers of each resort can be found in your PassPorter (on the resort's page) and online at AllEarsNet.com
HERE.
Eileen