Peel the mango and remove the fruit from the stone. Dice the fruit, and place on a flat pan. Freeze for about 40 minutes. Cut the grapefruit and squeeze the juice.
Add the diced mango and grapefruit juice to a blender with the ice cubes. Add the honey, and blend everything together. Taste, and adjust the sweetness with more honey if necessary.
Add 2-3 ice cubes to the glasses. Pour in the smoothie and serve immediately. Garnish with the fresh mint.