Wash potatoes and scrub off any dirt and grime. Using a sharp knife, score the skin all the way around the center of the potato while quickly twirling it around with one hand and keeping the knife steady in the other.
In a large pot, add potatoes, about one teaspoon salt, and enough water to cover. Over medium heat, bring to a boil and continue to cook on a gentle boil until fork-tender.
Remove from heat and drain well. Gently pull skins from both sides and discard peels.
Cut potatoes into 1-inch cubes and arrange in single layer on a baking sheet. While still hot, season with salt and pepper to taste and sprinkle with the vinegar. Refrigerate for about 20 to 30 minutes to cool completely.
In a bowl, combine mayonnaise, milk, dijon mustard, and sugar. Whisk until blended.
In a large bowl, add potatoes, eggs, bacon, celery, onions, and green onions. Add mayonnaise dressing and gently stir to combine.
Cover and refrigerate for about 1 to 2 hours or until completely cold.