I've had sex in various places that would make it easy to be seen. Which, in some cases, I have. Lets start at the beginning.
My first girlfriend I use to finger on the couch and play with her tits while her parents were in the bedroom. A room which was directly off of the living room.
Also fingered her while in the pool with her cousin and a few nephews.
Moving on to my second girlfriend, I had her flash her tits while we were walking through the parking lot up to the mall. It was night time, but the parking lot lights were on. No one was close by, but who knew if there was anyone in the cars.
Third girlfriend and I had sex in her mothers living room while her mother was upstairs.
We also sat naked in a hot tub together outside at night. Houses behind us and on both sides of us.
Now my fourth and final girlfriend. We've done quite a bit so far.
That same hot tub, we had sex in at about 9:30 at night. We were going at it for about half an hour with no care who we were seen by. I remember seeing a person standing in the sliding glass doors looking like they're on the phone in the house behind us and what looked to be a younger woman looking out through a different window. They were just shadows. I'm not sure if they called the police, because shortly after, we were spooked inside by a passing police officer with emergency lights on. We ended up finishing inside.
We've had sex on a picnic table off the nature trail of an elementary school. Don't worry, it was the weekend. I remember seeing a family out in the distance at the play ground while we were going at it. They had no chance of seeing us though.
We had sex on a small beach off of a back road at night. This one is risky as it's a hot spot for people to hang out at night. We were completely naked while doing it. Only one car drove by and didn't seem to notice. It was very late at night.
I've fingered her and played with her tits while driving at times. We were in a convertible with the top down. Night driving.
Once we did it in her grandmother's back yard while we were having a fire. This one was cut short when her neighbor came outside to walk her dog.
When we finally moved in together we used to have sex all the time in the living room with all the blinds open. We lived in a small community with about 5 small houses that could see us. The closest one being about 25 feet away. This house's kitchen window faces our living room. So the neighbor would be in the window for 10-15 minutes at a time washing dishes. I remember seeing her once do a double take, once she looked like she was pretending to clean the window, and once she even came outside to "look for something in her car." Which placed her about 15 feet from the window we were in. Another neighbor had a few friends over outside in tents. I swear I saw one of them signaling to us with a light.
My girlfriends sister moved in with us at one point. We would have sex in our bedroom, which is off of the living room, with the door wide open. Normally she just remained quiet and she couldn't really see us from where she would sleep on the couch, but the night before she moved out, I know I heard her moaning in the background while we were doing it.
We occasionally visit her cousin's place during the holidays and usually always end up having sex where ever we are at night. The two best times were when we were on an air bed positioned in front of a couch that her uncle was sleeping on. It was early in the morning and we were both on our sides with her back to me. We quietly slipped off our pants and slowly went at it. Being very careful not to make too much noise. Cut short when we started hearing the kids waking up. The other one was a similar situation. On an air bed but positioned behind the couch with a different uncle sleeping on it. We did it this time late at night and had a little more freedom with the movements in this situation.
Another time at her cousin's she gave me a blow job. Again, on an air mattress positioned in front of a couch with her mother "sleeping" on it. I put quotes around that because I'm pretty sure she was pretending.
Another time we had sex in my parent's pool during the day. A lot of cars drove by, but the only one who saw us was a truck driver. He hit the brakes pretty hard when he drove by.
I think that covers everything.