Cook unpeeled, whole potatoes in a large pot of boiling water for about 20 minutes. Test potatoes periodically with a toothpick until you reach your desired tenderness. The toothpick should insert easily through the center and you should see some slight crumbling. Do not overcook! Place potatoes in a colander to drain then set potatoes aside to cool slightly.
To make the dressing, combine mayo (or Greek yogurt), sour cream and garlic aioli in a small bowl and season with salt and pepper to taste.
Quarter the potatoes, and place into a large bowl. Add cheese, bacon, celery and green onions to the bowl and gently toss the ingredients together adding 1 tablespoon of dressing at a time. Serve immediately.