"¿Dónde se quedan ustedes?"
Translation:Where are you staying?
Theo, i have learned from doing these lessons and reading the comments that the best way to answer your question is to think of it this way. Everytime you see "se" someone is doing something or feeling something to or within themselves.
So in rhis case look at it like this. "Where do you keep yourself"
The question has been adequately answered already. My two cents' worth: One of the big things stepping outside of one's own language is recognizing that the rules for "reflexive verbs" is different in other languages. Also, from these lessons in Duo, it appears that Spanish uses the reflexive a lot more often than English or German. A lesson or two ago (from this unit), Duo mentioned cases in which "me," "te," "se," &c would be required in sentences but did not specifically mention that it was because these verbs were reflexive, per se.
I'm thinking that is where the confusion comes in. (I know it did for me)