I am a Japanese living in Beijing 10 years. I often go to Hong Kong (about once a two to three months) for biz trip. During my staying in Hong Kong, I use Mandarine or English to communicate with Hong Kong people, but I think I should study Cantonese for more good understanding Hong Kong culture and also want to pay respect to them. I speak Japanese and Mandarine, English is not so good at speaking (you can see my typing the above ).
Thanks for your attention.