I've done the movie theater a few times, but never during good movies. I can masturbate at home for free. When I spend $9 to see a movie I'm going to see the movie.
Once I tried it while out on the trails horseback riding, but the trail was a little tricky in spots and I had to concentrate on making sure the horse was going to the right direction.
I've also done it on the beach... MANY times. All I have to do is sit up, put a towel over my legs and go to town. When someone walks by I just smile.