Welcome to Hong Kong!
tl;dr
You can communicate without issue using English in Hong Kong. You can optionally learn (spoken) Cantonese / Mandarin as you wish.
English
First of all, you will have no difficulties using English in daily life, especially in university. Basically, everyone in university can speak English. Except, some professors / tutors from other countries speak English with dialects which maybe more difficult to understand.
Also, basically all Hongkongers under age 40 can speak English, as it is compulsory to learn in school. And actually many over age 40 speak English as well.
The spoken official languages of Hong Kong are Cantonese and English. (Hong Kong was British colony before 1997.)
Besides, most of the signs in public areas (like road signs) in Hong Kong are bilingual (Traditional Chinese + English). Some restaurant provides bilingual menus or English menu upon request.
So, no worries! There will be no problem using English in restaurants, shops and transportation. (Just don't speak too fast.)
Chinese
For Chinese, it is more confusing! These are the basic classifications of "Chinese".
- Written: Traditional Chinese, Simplified Chinese
- Spoken: Cantonese, Mandarin, etc.
Usage:
Traditional Chinese + Cantonese:
Hong Kong &
Macau
Traditional Chinese + Mandarin:
Taiwan
Simplified Chinese + Cantonese:
Guangdong province of China
Simplified Chinese + Mandarin:
Other parts of China
Simplified Chinese + Cantonese & Mandarin:
Singapore &
Malaysia
(Maybe someone can further clarify the popularity of Cantonese & Mandarin in Singapore & Malaysia)
Cantonese is the mother language of Hong Kong (as well as Macau). People speak in Cantonese.
Meanwhile, you will have no problem using Mandarin in Hong Kong as well (although most Hongkongers speak it less fluently).
What to learn?
Depends ;)
If you like to communicate well when having your Bachelor's degree / pursue your career in Hong Kong / Macau, I would strongly recommend you to learn (spoken) Cantonese rather than Mandarin.
Otherwise, if you will pursue your career in China / Taiwan, or prefer to communicate with mainland Chinese / Taiwanese people, you can learn (spoken) Mandarin.
Written Chinese is NOT really necessary in your case.
The course you have suggested will teach Mandarin Chinese. As said above, it will be still useful in Hong Kong.