Cut unpeeled potatoes into cubes. In a covered large saucepan, cook potato in enough boiling water to cover about 15 minutes or just until tender. Drain and cool slightly.
In an extra-large bowl, combine bacon (if desired), mayonnaise, celery, sweet pepper, green onion, peanuts, peanut butter, cilantro, parsley, and vinegar. Add potato; toss gently to combine. Cover and chill for 4 to 24 hours. Makes 12 servings.