If I learn Mandarin At City University of Hong Kong will I be able to use that Mandarin often in Hong Kong?

I am asking people who live in Hong Kong or take classes there if people on the street, in stores, or restaurants speak Mandarin.I know Cantonese is the official language I am simply asking that if I learn Mandarin in Hong Kong will I be able to use it outside the classroom?

If not I might go to polluted Beijing.