Yeah, with this line the author completely lost me. What did he expect them to do? Does he think of himself as steadfastly committed to not speaking Japanese, Bantu, Hindi, and Algonquin?
(I realize it was (hopefully) meant in jest-ish, but there are better ways to make the point.)
He expected them to speak the barest minimum of English, so speakers of Japanese, Bantu, Hindi, and Algonquin do not have to learn more than one foreign language when vacationing abroad.
Honestly, I myself learn one emergency phrase in the native language, "I am sorry, please repeat this as if I have a learning disability". Upon hearing this my vis-a-vis would either actually switch to a slow and dumbed-down register of their native language or realize they won't lose face by speaking bad English to me.
This might be a British humoUr thing - as a local it read very much as a self-deprecating jab at our own English-centric travelling. Taken literally obviously it would be offensive, but it's not meant that way. I note that the author lives in Edinburgh, a place which has a reputation for quite dry, understated and self-deprecating style to start with - understandably, as the only way to stand the hordes clogging the Mile and other picturesque spots.