In a Dutch Oven or 4 quart saucepan, bring about 10 cups of water to boil. Reduce heat to medium and add potatoes. Cook for about 3 minutes. Add Rotini to the potatoes and continue to cook about 15 minutes. Drain and rinse with cold water to cool. Drain well.
In a large bowl, combine the cooked potatoes and rotini, bell pepper and onions.
In a small bowl, combine the dressing ingredients and blend well. Add to salad, toss to coat. Cover and refrigerate at least one hour or until serving time.