Place half of the potatoes and 1/4 cup of the water in 2-quart microwavable casserole. Cover and microwave on High 10 to 12 minutes or until potatoes are tender; drain. Repeat with remaining potatoes and water.
Mix mayonnaise, sour cream and salsa in large bowl. Gently stir in potatoes and remaining ingredients.
Cover and refrigerate at least 2 hours until chilled.