Pirkey Avot: How to Speak in Front of Guests

Rav Chaim Palagi (1) rules that one may not speak in a foreign language when one has a guest in the home.

The reason is, the guest might feel that they are speaking about them. And this is not Derech Eretz, a proper was to act.

This is why those who live in the home should speak in a common language.

If there are those that need to be spoken to in a different language, the guest should be made aware of it before speaking to them, and should ideally translate to them.

If it's not possible to translate to them what was said, if it's private information etc, the guest should be understanding and forgiving.

Sources:

1. Kaf HaChaim Palagi Siman 5:14