I have some firsthand info! In 1998 I visited MK, Epcot, and MGM with a visually disabled friend who uses a service dog. My friend stayed at the CBR, and they easily accomodated his request for a room near the bus stop.
The dog was welcomed pretty much everywhere. There are backstage areas he was allowed to take the dog to for "potty stops". Guest services in each resort were wonderful about supplying info. They also had braille guides, although I believe they request a deposit for them.
The dog was NOT at all welcomed on Peter Pans Flight in the MK. The CM was downright rude about it. At Alien Encounter, the dog wasn't allowed in during the show, however the CM's allowed my friend to be escorted to his seat with the dog, and then they took the dog out. As soon as the show was over they were right back with the dog, making jokes about how much she loved belly rubs
At all the restaurants they brought out treats for her. My friend carried a collapseable water bowl to give the dog a drink every hour or so, but we were there in January and it was rather cool.
At many attractions the disabled seating is in the back. We explained to teh CM's that my friend had a very limited amount of vision, and asked to be seated in the very front. The requests were always granted.
If you have any specific questions, please feel free to ask.
Anne