"I expect to have to knock on their doors anyway, just in case. "
Very wise. A teenage friend had a tale of the day he was getting a BJ from his girlfriend. Then his mother and her mother walked into his room. Fortunately they left immediately - as they had been under no illusions about what the young couple probably did.
Unlike a neighbour. One day her young teenage daughter and a boyfriend were "at it like rabbits" naked on their lounge floor. In that position they believed themselves shielded from external view by the frosted glass in the bottom section of the floor to ceiling windows. Unfortunately the room was brightly illuminated by the evening sun - which made them very visible outside even through that glass.
A quick word to her later appraised her of the problem of that location. She didn't even blush - but went "Oops!".