I've met people who did well in Hong Kong for decades without learning the local language (Cantonese) and then haven't bothered to learn Mandarin since China took control 20 years ago.
It's pretty doable in Sweden, too. In Japan, Russia or Argentina, though, you'd be at an enormous disadvantage.
To be fair, HK is bilingual, at least in the sense that all government/utility/etc. forms are available in both Cantonese and English (these days also in Simplified Chinese).
Article 9 of the Basic Law stipulates:
"In addition to the Chinese language, English may also be used as an official language by the executive authorities, legislature and judiciary of the Hong Kong Special Administrative Region."
So, it's quite easy to get along without Cantonese or Mandarin (or without English, for that matter).
However, without Cantonese, one only has limited access to what's going on in politics, civil society, show biz, etc.
It's pretty doable in Sweden, too. In Japan, Russia or Argentina, though, you'd be at an enormous disadvantage.