When I go to settle in Hong Kong, is it better to learn English or Cantonese?

You have to learn both. Cantonese is the local language. It is very useful no matter where you are. And the local area is sometimes quite exclusive. The local language can bring you closer to the locals.

Hong Kong was once a British colony. For a long time, senior officials spoke English, and some schools now require all-English teaching in junior high schools, which proves that Hong Kong people attach great importance to English, and Hong Kong people like to speak Cantonese with English words mixed in. This is already their language habit and it is also a cultural heritage! !