I have a disability myself. I'm not intellectually impaired, but at times do have a hard time remembering faces, especially if I haven't seen them in awhile. I also have worked with a few people who have various degrees of intellectual disabilities. In terms of this particular situation, I think the OP was just a little harsh. Not much as I totally understand the feeling of being harrassed by a guy with "issues" when I jusr want to be left alone. I certainly don't think she had to engage in conversation. My tactic usually is to tell someone I'm really into my reading material. If I didn't have a book or magazine, I would say just that I dont feel like talking. Then if he persisted, I would definitely tell the receptionist or whoever. He just may not remember the OP.
I actually used to volunteer on a hospital ward. I had EXTENSIVE training and if on the ward and someone said they were busy or didn't want a volunteer in their room, would immediately leave and not be the least bit offended. (I didn't need training to know that, lol.) I also didnt go in the room if visitors, a nurse or doctor was in it, unless the patient indicated they wanted that.(Most of these patients were there longterm, so sometimes they wanted me there.) I agree with others that it seems odd,that there would be a volunteer in a doctors office. It does seem kind of like his parents finding a way for him to contribute. It is a noble idea, but probably not the best idea.
And just read your reply jane7166, and totally agree. The program does sound pretty poorly run. in the long run, it may do harm than good, if people get a negative view of people with intellectual disabilities.