My ex was stationed in Germany in the early 80's. He became quite good at speaking German and would often go into towns when on leave. He said many of the soldiers were afraid to venture off the base.
When we lived in Uganda almost everyone we dealt with could speak English. Many sellers in markets or people in rural areas couldn't speak any. We had someone tutor us in the local language so we knew a lot of words and phrases but never became fluent. It was fun to speak it to people who didn't know us. It was assumed that all white people are rich so we were often asked for money. Walking down the street one day a group of young guys said 'mzungu, can you give me money'. We knew the word for 'no' which was somewhat less than polite and we replied 'ngaha' and they thought it was hilarious that we knew this word!