Leaving shrimp whole makes the presentation of this salad especially beautiful; they can also be chopped and mixed in.
Heat oven to 400 degrees. Place shrimp on a baking sheet coated with olive-oil cooking spray. Sprinkle with 1/4 teaspoon salt and 1/4 teaspoon pepper. Place in oven, and roast until opaque, about 8 minutes.
Zest limes; squeeze to yield 1/4 cup juice. Combine lime juice, zest, olive oil, cilantro, and remaining salt and pepper. In a bowl, combine 2 tablespoons lime dressing with shrimp; toss to coat. In a large bowl combine mangoes, cucumbers, red onion, jicama, and remaining lime dressing; toss to coat. Divide salad and shrimp among six bowls. Garnish with remaining cilantro sprigs, and serve.