I wonder if people who are mentally challenged know that they are challenged and have you ever looked in the mirror and wondered if you are?

Pretty much all autistic people I know (and I know a lot since my parents work with them and I'm part of a group of highly-functioning autistic students at my school) are completely aware including myself, since I was about 11.

Yeah, their was this one disabled girl who communicated through writing and it turns out she is well aware of her surroundings and that she is mentally challenged

Yes, they know. I have friends in the Autistic spectrum and they're all perfectly aware. I have another friend with dysphasia and she's always been aware.

yes they do. Everyone has some sort of mental challenge somewhere.

they know.

I've worked with special adolescents and adults. They're definitely aware.