We were just there last week and saw them both at MGM. Got a cute picture - Sulley will squat down for the little ones - he's TALL!!! I don't know about autographs, though. We were second in line after the door opened, and I didn't have time to find the book and pen. But, they probably would. They might not sign, just stamp, but it's something.
I'm not exactly sure where they were, but they were in a little hole-in-the-wall kind of place. It had a kind of roll-up garage door. The door rolled up, and there they were!! They were both 'real' characters, too! Walked around, etc. I'm thinking we saw them somewhere near where Buzz/Woody/Jessie were, but I couldn't swear by it. Hopefully a CM could help you.
But, for sure, they ARE at MGM!!