Bring large pot of lightly salted water to boil. Add whole potatoes, and cook until tender, 15-10 minutes. Drain, run under cold water to cool, and chop into 1 inch cubes.
Transfer to a large serving bowl, and refrigerate until completely chilled, about 2 hours.
In a small bowl, stir together the ranch dressing mix, mayo, and green onion. Cover, and refrigerate for about 2 hours to blend flavors.
Cook bacon through one of the following methods: fry, microwave in paper towels until crisp, or my favorite bake in the oven until crisp. Cool, Stir the mayo mixture into the potatoes. Crumble bacon into the bowl & stir to distribute.