Preheat oven to 400 with rack in center of oven.Combine all dry ingredients in a bowl.Make a well in the center of the dry ingredients, place drained pineapple, diced mango, yogurt, eggs and oil in the well. Or just mix the wet ingredients in a separate bowl, then pour all at once into the dry ingredients. Fold the wet ingredients into the dry, just until the flour disappears. Do not over mix.Scoop the batter into a muffin tin that has been greased or lined with cupcake liners. Fill muffin tins about ¾ full. Sprinkle with sugar if desired.Bake for about 15-18 minutes or until tops are golden and muffin springs back when touched lightly.Makes approximately 10-12 muffins.