From my experience, its quite acceptable that Asians speak English or other European languages with each other, however, to the typical Chinese it would seem quite funny or even ridiculous that that 2 Caucasians speak to each other using only Cantonese in social or day-to-day contexts.

I hope that one day it will be considered normal when 2 white guys speak Chinese to each other in Hong Kong, just like its normal that 2 Asians speak English to each other in Australia.

One or both could easily be non-English speaking, but from my observations the following is likely to happen if such a situation actually took place in Hong Kong:

1) the average person would look twice;
2) point and/or stare;
3) make comments such as “why don’t you speak English? You are both gweilos”

Video: 1:47min