I never tell professors...or anyone...unless there is a good reason, but then again, I'm a very private person. Has saying things you feel are out of place been a serious issue in the past? If you think that its going to hinder your academic success in the class, then maybe it would be best to talk with your instructors. Keep in mind though that not everyone will be understanding and some might not even know what having ASD means.
My school has a disabilities office that is amazing. They notify the instructors prior the the start of the semester of disabilities and any extra services you may need (extra test time, excused absences for med reasons, etc). Do they have anything like this at your school? That would probably be the most ideal route.