Taiwan and Hongkong Travel

I usually like to learn some basic phrases in local languages when traveling to make my life a bit easier. I am traveling to Taiwan and Hong Kong soon, and I wonder if I should learn Cantonese or Mandarin. I already learned a bit of Mandarin when I traveled to China recently, but I’m wondering if I should continue practicing it more or switch to Cantonese since I heard it’s more commonly spoken in these destinations.

I would love to hear input from locals who live in these two places. Thanks so much in advance!