厕所：toliet ,it's an oral coarse word , I would use 厕所 when I am with my friends. it's kinda joke 洗手间，卫生间，休息室：restroom, I normally use these words when I am with clients/strangers/not familiar friends 浴室，洗澡间：bathroom, the place where u can have a bath or just XX

I think bathroom is better.you can say "can i use your bathroom"?我可以用一下洗手间吗？ Actually bathroom have many meanings.like厕所，卫生间，洗手间。you can use any of them. Hope that helpful to you

厕所，洗手间，卫生间 are fine for all occasions.

ok! :)

When you want yo ask where is the bathroom, actually,you can use厕所 洗手间 and 卫生间 . But there's difference. 洗手间（bathroom）is a nicer way of saying 厕所（toilet). 浴室and洗澡间are where you can have a shower. So it'e better for you to ask 我可以用一下你的洗手间吗 when you want to use the bathroom.