An Argentine or Mexican tourist in Madrid, or A Brazilian tourist in Lisbon, will certainly hear phrases he has never heard before and may find some of them offensive. I myself have a list of Portuguese colloquialisms which may embarrass an uninformed Brazilian during his first trip to Lisbon. Likewise, there are slang words and phrases that may embarass or sound offensive to a native speaker of the English language visiting another country, if he has never heard them in such contexts. e.g.
- A California girl to an English lady: "Oh, shut up!"
- A Londoner to a young man in Kansas: "Will you have a fag?"
I don't expect swearwords or an exhaustive list, and I don't mean the knowleadgeable and well-informed tourist either. This type of person certainly knows most foreign colloquialisms.