Yes, it is bitter. I think Papait is not a popular/common vegetable, I think only us "Ilocanos" eat it in our country.

By the way, I have done a search on Google using the keywords "papait ilocano delicacy" and it returned significant results here's an example https://pepaysfoodiesandtravels.blogspot.com/2013/03/papait.html

And you can see my search result here https://www.google.com/search?q=papait+ilocano+delicacy&oq=papait+ilocano+delicacy&aqs=chrome..69i57.8213j0j1&sourceid=chrome&ie=UTF-8