Not so much public, but during work (a route job) I had to rub one out (on more than one occasion) in different facilities' restrooms. And during my long drives in the car (not always so easy.
Only once when I was 15 while out dirt bike riding. Loved the feeling of the breeze and warm sun on my cock...
I've done it a lot. But never with the purpose of getting caught. I masturbated a lot at work when I had to work late. In nature when I was was hiking. But the most memorable time was in a parking garage while I was in my car. We had a really good looking internship worker that day. She was really hot. My wife never had a problem with me looking at other women as long I didn't touched them. This girl was definitely going to be a character in my next wet dream. When I got to my car I already had my zipper down and my cock out. There weren't any other cars near to me so I decided to go for it there and not waiting for me to get to a more abandoned place. With the hot looking internship worker on my mind I started to stroke myself. I got so excited that I forgot everything around me. When I finally shot my load in a paper coffee cup. I noticed that there was a mobile home standing next to me. A middle aged couple was looking at me and had at least seen a part of the show. I never noticed that they had arrived. When I nervously smiled at them they both gave me a thumbs up. I took my cup with cum and held it up and thanked them for not calling the authorities. The woman made a suggestion with her hand that I needed to drink the cup. I've had done it for God knows how many times so I gulped the cum in one go. The woman started clapping exited and said something to her husband. I didn't wait for them to come over or anything. I started my car, waved at them and got out of there.
I had an experience on a hotel balcony a few years ago (there was a girl on the balcony opposite doing the same thing). I've wanked at work in the toilets if that counts. Quite a few times I've teased myself on the drive home from work an pulled into a layby to finish off...always feels really hot driving the rest of the way home with cum soaked boxer shorts!
I have done it at work in the restroom a few times. Heck I even had sex once with my wife at my office desk .
I have often masturbated in a public place, especially public toilets, and not always in a cubicle. I often go for a walk in the woods, go behind a bush and have a wank. I always make sure there are no kids about. I do it when they are in school or late at night. I have been caught a few times, usually by guys walking their dogs.
I masturbated regularly in the toilets when I was at school, also at work in the toilet, and on a intercity train sat in my seat under the table with 2 gorgeous girls sitting at the table in front of me, I don't know if they saw anything with my reflection in the opposite window to me, it certainly made me cum so hard with the excitement of the idea that they might have seen me.
I often go for a walk in a spot near where I live that is a popular cruising area for gay men. I masturbate quite openly and have enjoyed many mutual wanks with guys.
I also rubbed my cock thru my pockets in class, have JO'd in work vehicle, public restrooms & parks & video booth booths & movies.
I enjoy it on a long road trip. There is one spot I have always love to jacked off on. It is on I-20 west, as soon as I cross the Louisiana line from Mississippi. So, i start at the end of the river bridge and try to cum before the bear crossing sign. I am so glad I bought the Weather-Tech floor matts....lol
It is dicey, that's what makes it so exciting. The thrill of being caught adds to the pleasure. Only make sure there are no kids about.