1In 3-quart saucepan, heat 1 inch water (salted if desired) to boiling. Add potatoes. Cover and heat to boiling; reduce heat. Simmer covered 20 to 25 minutes or until tender.
2While potatoes are cooking, in tightly covered container, shake all dressing ingredients until blended. Drain potatoes; cool slightly. Remove skins if desired. Cut potatoes into cubes (about 4 cups).
3In large bowl, pour dressing over warm potatoes. Add cucumber, bell pepper, onions and tomato; toss to mix. Serve immediately, or cover and refrigerate 1 to 2 hours until chilled. Stir gently before serving. Garnish with cilantro.