Nope.
Generally they're pretty careful when and where they do it if there's a chance they could get seen. They're no stranger to the allure of risk and doing it somewhere public, but they don't just get down and do it in the open. Usually they look for at least some kind of privacy before they have sex. The riskiest and most open they've done was during a bus ride. There it started with Vivi "dropping" something below Kai's seat and then deciding that his lap might be comfier than the bus seat. Then they let the bumps in the road do the rest~
But no one caught them then, they made sure to inconspicuously block all sightlines to what was actually going on.

Though, I guess Stacy did catch them in the middle of it a few times, but I wouldn't really count that since they're all together and no one was really bothered by it. For them it's more like walking in on your roommates just playing a game together or something rather than a "OMG you guys are having SEX?!?!" moment.