Cook potatoes in boiling salted water to cover 30 minutes or until tender. Drain and cool slightly. Peel and cut into cubes.
Sprinkle potatoes evenly with 3/4 teaspoon salt. Pour 1 cup dressing over potatoes; gently toss. Set aside remaining dressing. Cover potato mixture; chill at least 2 hours or overnight.
Arrange salad greens evenly on a large serving platter. Peel and chop avocados; toss with lemon juice.
Arrange potatoes, avocados, tomatoes, and next 4 ingredients in rows over salad greens. Sprinkle with pepper. Serve with remaining dressing.