I am British born Chinese. My Cantonese is dreadful, to the point it is embarrassingly bad, so I tend to stick with English when visiting Hong Kong. If I go to a shopping mall in Hong Kong Island or central Kowloon I have no problems communicating as English will be widely spoken. But go out of the main tourist areas or even taxi drivers in the central area then English will not be commonly well spoken.
When I was a kid I remember the BA flights to HKG always had crew who spoke my mothers language which she really appreciated.