When I was very pregnant my then husband wanted to have sex in a field of beautiful wild flowers. I said no because at that point I didn't want to have sex anywhere as I felt like a fat cow. Other than that outdoor sex (as a teen and then later as an adult) was always fun and frankly I never cared about who saw us. On the beach actually not very comfortable because of the sand. Group sex...just ew. But I am pretty traditional about one-on-one hetero sex.