Well it is good that you are open-minded and love the rural areas. I would give Mindanao a shot, if I were you.
As VetR stated, it is pre-dominantly Catholic, but it still has the muslim faction.
It is cleaner that other places in the Philippines, the people are quite friendly, you have the lovely sea ways, as well as the provincial areas and the food is fresh and inexpensive.
I would have stayed there, if not for my significant other's parents giving me bad advice and the fact that I can became obligated to many different projects in the area that I reside now.
I will return to the U.S. to visit my family, after residing here for 11-years and other places for 5-7yrs. I am due to spend physical time with them, but will probably return to the Philippines and then it will be time for new beginnings...most likely Mindanao.
Whatever your decision, I hope you will enjoy your retirement years of life.