Peel and seed papayas; cut lengthwise into 1/2-inch-thick slices. Peel and rinse jicama; cut into matchstick- size strips about 1/8 inch thick and 3 inches long. Pit and peel avocados; cut lengthwise into thin slices.
In a small pitcher or bowl, mix orange juice, lime juice, rice vinegar, and salt.
Arrange papaya and avocado slices on a rimmed platter. Top with jicama and drizzle with sour orange dressing.