Unfortunately I've never done anything as public as I dream of, but my best friend and I did have sex in his very open back yard in full view of a crowded bar that was right across the street from his house.
It was a saturday night and I was hanging out drinking with my friend, his wife, their neighbor, and another girl I didn't know very well. After a lot of drinks and me trying my best to look cute for my friend, he gave me the definitive "i'm going to wreck you" look and we decided to go out to his back yard and smoke a joint. Unfortunately the neighbor who was drinking with us smoked too, so we couldn't be alone outside for at least 20 minutes. Once the neighbor went inside to use the potty, we immediately started to make out. About 5 minutes in it was just too much to handle and I got to my knees and went to town on his cock. This didn't last long and I was soon bent over the railing on his deck and had his cock buried in my ass. I could see people entering and leaving the bar across the street, but I don't think anyone noticed us. If they did they kept quiet about it. He finished in me as usual and we went back into the house like nothing happened.
It was easily the best sex I've ever had and I'd do it again in a heartbeat.
