It is different if you are in a shop or on a bus, train, etc., where you have no ongoing relationship with the employees or other shoppers/service users. But if you are at work you have colleagues with whom you interact on a daily basis, and I think it is insensitive, if not rude, to speak with one or more other people in a language that you know other colleagues don't understand.
The land is dry, and the people are ...stupid?
Richard E Grant's Very Modern Odyessey
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I think the look on my face told him all he needed to know.
