Wash potatoes and boil with skin on for 15-20 minutes or until almost tender. Remove from heat and drain. Cool. Cube and hold. In a bowl, whisk together yogurt, mayonnaise, vinegar and pepper sauce. Stir in cranberries and let stand 20 minutes to soften cranberries slightly.Stir potatoes, cucumber and scallions into yogurt-cranberry mixture and toss to coat. Adjust seasoning as needed. Cover and refrigerate at least 1 hour before serving.