Working with mentally disabled (LFA, Downs, CP, etc)
I agree with those who say it depends. I think aspies are more likely to find LFAs easy to understand because many of the same traits are present in aspies and in LFAs - just a lot more pronounced in LFAs. And many mentally disabled people who don't have an autism spectrum diagnosis nevertheless have some traits, for example I know a guy with a diagnosis of mild cognitive disability who stims, has obsessive interests (insects and crawly things) and talks in an odd tone of voice. I've asked his Mom if he has AS, and she's said he's not diagnosed as being on the autism spectrum, just cognitively disabled.
With non-autistic mentally disabled people, they can be hard to read for the same reasons that NTs are hard to read. But many of them will act a lot like an NT kid a lot younger than their actual age, and many aspies get along better with younger kids, so they can be easier to read than NTs as a result. They also tend to be more forgiving of social mistakes in others, partly because they may not be aware you broke a social rule, and partly because they know what it's like to misunderstand things and make mistakes even if they wouldn't make the kind of mistakes an aspie makes.
Actually, what I personally find hardest isn't dealing with the mentally disabled people themselves - it's dealing with the program coordinators, the other volunteers/workers, and the parents. (Of those three groups, the parents are the easiest to get along with, because most parents, if you show that you respect that they know their own child better than you do, will appreciate you taking the effort to help their child.)
About the only really serious aspie-related problem I've had with relating to a kid in one of the programs I worked with is that not being able to follow eye gaze well is a serious impediment to talking to a child who uses eye-pointing to communicate. (Technically this kid wasn't mentally disabled, just very severely physically disabled, but he was in a program where most of the participants had mental disabilities, and he used to be thought to be mentally disabled because of the impact his physical disability has on communication.)
Depends how you define the term. I've seen the term 'mental disability' defined in two different ways.
One definition is as a more politically correct synonym for mental retardation, which is defined by an IQ below 70. By this definition, probably the vast majority of people on this forum would not be considered mentally disabled. (I'm sure there are a few, though.)
The other definition would be 'a disability that affects the mind', regardless of IQ score. By that definition, yes, aspies would be mentally disabled.
A lot of the terms are inconsistent, because many people call different things by the same name (in UK learning disability is IQ <70, in US it's a specific difficulty with certain academic subjects) and because people keep deciding the current name for people with an IQ below 70 is offensive and changing it to something else in the hopes that calling it by a different name will magically erase the stigma of the condition.