Here's some info based on our experiences.
ASL interpreters are available at certain shows/attractions on certain days of the week at each park. The link above tells you which day. If you contact that number they can email you the schedule the week before your trip. If you go to
www.wdwent.com and look at the shows for each park, they will tell you the schedule for the current week to give you an idea of the times and where to go. I always get the schedule at Guest Services as well when I arrive at the park. Interpreted shows we have seen:
MK: Dream Along with Mickey, Move it Shake it Celebrate it Parade, Monster's Inc. Laugh Floor, Celebrate a Dream Come True (3:00 parade to be replaced) and Jungle Cruise.
AK: Flights of Wonder, Finding Nemo the Musical, Jammin' Jungle Parade, Festival of the Lion King
DHS: Beauty & the Beast stage show, American Idol, Indiana Jones Stunt Spectacular
Epcot: Turtle Talk with Crush and sometimes other things by the tank there but we have not seen these.
The ASL interpreters we have met are AWESOME!
If your son can read well, the handheld captioning device may be a good option when there is not ASL. My husband is HOH and was surprised at how much he had been missing before he got this. This is info I got from the Guests with Disabilities dept.
Handheld Captioning: Portable captioning system that utilizes Disney's Handheld Device to display text in locations such as moving attractions. Devices are available at Theme Park Guest Relations locations and a $25 refundable deposit is required (device must be returned on the same day for refund). Available at the following locations:
MAGIC KINGDOM Park:
Walt Disney World Railroad
Adventureland (2)-Pirates of the Caribbean, &
Walt Disneys Enchanted Tiki Room
Liberty Square-The Haunted Mansion
Fantasyland (5)-Peter Pans Flight, its a small world, The Many Adventures of Winnie the Pooh, Enchanted Tales with Belle & Under the Sea Journey of the Little Mermaid
Tomorrowland (4)-Stitchs Great Escape, Tomorrowland Transit Authority PeopleMover, Walt Disneys Carousel of Progress, & Buzz Lightyears Space Ranger Spin
Disneys Animal Kingdom Theme Park:
Camp Minnie-Mickey-Festival of the Lion King
Rafikis Planet Watch-Wildlife Express Train
Epcot®:
Spaceship Earth-Spaceship Earth ride
Universe of Energy-Ellens Energy Adventure
The Seas with Nemo & Friends-Seas with Nemo & Friends ride
The Land-Living with the Land
Imagination!-Journey Into Imagination with Figment
Norway-Maelstrom (ride portion only)
Mexico-Gran Fiesta Tour Starring The Three Caballeros
Disneys Hollywood Studios:
Beauty & the Beast-Live on Stage
Star Tours The Adventures Continue
Indiana Jones Epic Stunt Spectacular!
The Great Movie Ride (ride portion only)
Disney Jr. Live on Stage!
Walt Disney: One Mans Dream
Studios Backlot Tour
On Toy Story Mania ride there is a "CC" button right in the car which will turn captioning on for you.
Also keep an eye on CM's nametags because if they speak ASL it will be noted on their nametag.
Hope this helps.