Arrange potatoes in an even layer in a 15- x 10-inch jelly-roll pan. Coat with cooking spray, and sprinkle with 1/2 teaspoon salt.
Bake at 400° for 25 minutes or just until tender. Let cool slightly.
Stir together remaining 1/4 teaspoon salt, celery, and next 9 ingredients in a large bowl until blended. Add potatoes, and toss gently to coat. Sprinkle with crumbled bacon, if desired; garnish, if desired. Serve warm or chilled.