Generally we assume that the students know at least some English in international beginner groups where they want to learn a new language. It is clear that the teacher communicates in the group in the language they learn, however, sometimes it is necessary to translate a phrase into a language the students know if that phrase is difficult to understand in the target language. I studied French some time ago and the teacher insisted that we use only French, and it worked well but we all felt confident because we had two more languages in common. Also I learned German and the teacher used only German, but when a student translated a word into English (we all knew English), the teacher nodded to indicate that we have understood the word correctly.
At the moment I see that I'll have a group where I'll have to teach a group of beginners with no other language in common, not even for the feeling of confidence.
Dear colleagues, what is your experience?