I know that Cantonese is the main spoken language and English is also an official language. Although I am chinese, growing up in the US, English is my first language. I can't speak or understand Cantonese (unless is is spoken extremely slowly) but am able to make my way through a conversation in Mandarin. I also can't read chinese except for numbers and some of my favorite dishes.

When speaking to locals, should I try to speak in Mandarin? or am I better off just using English? I head read that Mandarin is not too common in HK (I don't know how it compares to English) and sometimes speaking Mandarin can be a negative.