I live in Hong Kong, am non-Chinese (a gweilo) and speak Cantonese in everyday life, having grown up in Hong Kong. I often come across other non-Chinese people in Hong Kong, especially South Asian or other Asian service workers, and my instinct is always to speak Cantonese to them (for context, I do not live on Hong Kong Island, and rarely encounter other gweilos in my day to day life). The same is true of Japanese and Koreans who have lived in Hong Kong for a while. The vast majority of the time, the people in question will respond in Cantonese, and I can tell that, like me, they are not native speakers.
I'd be interested in what people think about the use of Cantonese as a truly multi-racial language of communication in these contexts, and whether other people who are visibly not Chinese have had similar experiences. When I have these encounters, me and the people involved never remark on the fact that we are speaking Cantonese, but I can often detect a subtle note of shared pride that we make use of the language of Hong Kong to communicate. Other people that I know are more skeptical - they say the obvious thing would be to speak English. For me, the more Cantonese is spoken in Hong Kong, the better. It's a matter of instinct for me that when I am out and about in Hong Kong, the language should be Cantonese.
Is this common for other people in Hong Kong? Does it happen in other contexts, like the US/Canada?