Despite the length of the British colonial presence in Hong Kong, it is not safe to presuppose that English is universally spoken.
Of course, amongst the staff of the larger corporations, the bulk of employees will have a very high level of fluency in English (as well as quite often another language.) However, amongst the employees of smaller firms, the foreign language levels can drop quite rapidly. Be prepared for some communication difficulties and do not assume that what you have said has been fully understood. Check for comprehension by asking lots of open questions and then go over points if you feel that there might be an area of confusion.
The Hong Kong Chinese can be much more direct than many other Asians – possibly as the result of centuries of Western influence – and that directness can come as a shock to those more used to dealing with countries such as Japan or Taiwan. This directness is most likely to be used at peer level discussions and it would be unusual for lower ranking employees to be overtly direct with more senior colleagues or visitors. Indeed, as has already been said, it can be difficult for more junior people to deliver bad news up the chain, which can result in all kinds of problems later in the proceedings.
It is important to show an interest in issues outside the business domain, so questions about family and health are good icebreakers. Issues around the current internal political situation in Hong Kong are probably best avoided until a very strong bond has been developed.