I have adapted a bit the options to suit Lexico's ideas.

I didn't mention whether they should ask "Do you speak Japanese" in Japanese or English, but it doesn't really matter in term of concept. What's more, some Japanese (especially older people) might not even ask that simple question in English.

I have added "or speak more slowly" in addition to gestures, in case the person doesn't understand. The idea is that they first speak in normal Japanese, assuming that the foreigner can understand.