The post office does not recognize Disney roads (since it is private property) so if you are mailing a letter through the regular mail you would send it through the Disney PO Box...Which takes a little longer to arrive (so give it enough time)
For regular US Mail you would send it to:
The guest name / Resort guest
C/O Disney's Animal Kingdom Lodge Front desk
PO Box 10,000
Lake Buena Vista, FL 32830
If you want to use Fed Ex, UPS, DHL, etc you can send it direct to the hotel at:
The Guest name/ Resort guest
C/O Disney's Animal Kingdom Lodge Front Desk
2901 Osceola Pkwy
Bay Lake, FL 32830
(407) 938-3000