I do not know. The gf I went with was kinda embarrased and shy when it came to that stuff. She was fine with freaky stuff, just not splayed out in the open, so we kinda stayed away from the resorts and explored the island mostly in the day.
I do know at the resorts things can get a bit heavy, so I'm sure you cold pry "get down" in or near the park. Also, at night time it was much more open when the kids went to bed.
Jeju, is a pretty island and it is more open (as in public) about sex then the rest of Korea. But I still prefer the mainland for living and sex life. Then again, all this information is spent on me being at Jeju for 3 days in 2006.