ProjectFi in mexico

I currently am thinking about switching to google fi, but I visit mexico very often(the part of mexico I visit is green so there should be no problem in theory) and I'm wondering if I am able to call mexican phone numbers without much problem or without extra fees when in mexico?

I don't mind being charged extra if I am calling from the US, but if I'm in mexico would I still be charged?

What about receiving calls (specially if I am in wifi in mexico)