Place potatoes in a large saucepan and cover with water. Bring to a boil. Reduce the heat to low. Cover and simmer for 15-20 minutes or until tender. Drain and refrigerate until cooled.
In a large bowl, combine the chilled potatoes, bacon and onions.
For the dressing combine guacamole, sour cream, milk, mayonnaise, mustard, salt and pepper. Mix together until well blended.