Wouldn't be surprised if they did what some drive ins have done: broadcast sound from the movie on FM or AM (and I guess they could have a radio in the motel rooms...or, yes, a speaker...)
love the drive in! this set up sounds really cool too!
took the kids a while back and they did have an fm broadcast
of the sound there. two screens too! so next time we're
parking in the middle. kids wach one screen with the speaker,
we watch the other out the other side with the car radio. it's
really a great way to take the kids to the movies and be a bit
more comfortable. cramming in a theater with tons of others
just isn't great for us.