I jerk off in stalls around my campus all the time.
On occasion it might be the (public) bathroom in my dorm at 2 or 3 AM, if I'm really horny and my roommate is awake. Depends on if any of the stalls are clean enough.
If I ever get horny in a night class (which run for 3 hours), I'll head to the bathroom at the break and sit on the can like I have a stomach ache. This is the time when EVERYONE is going to the bathroom so I sit and wait. Then when class starts again, I'm still in the bathroom with a 'stomach ache'. That's when I get my release.
There is one bathroom on campus with multiple stalls, and the one at the very end has a small hole in the wall. Not enough to stick your dick through, but enough to see the dick on the other side. I was jerking off in that stall one night, about 7 PM. Someone came in and sat in the stall next to me, while I'm in the middle of my business. This is what I always dreamed of, but I got really nervous. He tapped lightly on the wall and I could see the light disappear from the hole - he was watching. I mustered up my courage and began jerking off for him. I heard him moan every so often, and he tapped whenever it was my turn to take a look. It was exciting to watch and be watched, and for people to come in and have no idea what was going on.
Eventually he quietly asked to suck me off, but I thought it was too risky, even though I really wanted him to. I said no, blew a giant load...and he left.