Chinese Filipinos usually speak Fukien if they speak Chinese at all. Fukien is the language spoken in Taiwan, so it is good for business too.
My Filipina sister-in-law speaks Fukien, which she learned in her family, But she speaks some Mandarin as well.
She works at an international airport shop so the more languages she can speak, the better.
Basically though, I advise that you choose the language that 1] You know somebody who will speak it with you and/or 2] You will have more use for.
I'd say if you want to talk to Chinese Filipinos, Fukien is better. But if you think Mandarin will be of more benefit to you, then that would be your choice.
You WILL need people to talk with, to help you master the pronunciation.