In Hong Kong, Cantonese is/was the predominate dialect spoken. In more recent years, Mandarin has slowly been infiltrating society, with all the mainland Chinese people heading down there. (I can't understand Mandarin and it's hard for me to wrap my head around it.) Written Chinese is universal and can be understood by everyone even though there are hundreds of dialects spoken throughout China.

Considering the time frame, Kun and Lee would indeed speak Cantonese if they were from Hong Kong. So the words from the conversation during the Hong Kong tea early on back in Part 1 were correct. I easily picked up on fung zao, bau, gow and of course, Dai pai dong and nai cha.