All Disney resorts accept faxes for room preferences. The only resort that you can't will be the WL and all DVC resorts.
Because the resorts download the reservations from the central resevation system 1 week prior to your arrival, I recommend that you send the fax like 3 or 4 days before your arrival but not more than 4 days (because of past experiences). Send the fax to " Attn: Room Assigner" .
Don't attempt to send the fax more than 4 days before your arrival because sometimes the resorts don't have the reservation in their system, that's why I recommend you to send it exactly 3 days before arrival.
Have a nice trip!!!!