Hi, Susan!
Trained service dogs are welcome at most locations throughout Walt Disney World. I am not aware of any forewarning that you will need to give regarding bringing your service dog along with you. Keep in mind that you must have control of your pet at all times and it should be kept on its leash or harness.
You many want to read more information on
Service Animals. Here you will find detailed information on the parks, attractions, and relief areas for your service dog.
To put your mind at ease about bringing your service dog along to your dining experiences, after booking all your reservations online, give a call to (407) WDW-DINE (407-939-3463). You can let them know of your companion. If needed, they can make a note on your reservations.
Wishing you (and your wonderful service dog) a magical vacation!
Cathy