Heat grill. Fold four 18-inch-long pieces of foil in half; unfold and coat inside with cooking spray.
Place 2 cups spinach in center of 1 half of each piece of foil.
Combine couscous with 1/4 cup water; divide evenly among packets, placing on top of spinach.
Combine shrimp, 1/4 cup cilantro, oil and 1/2 teaspoon salt in a bowl. Divide shrimp evenly among packets, placing next to couscous. Fold foil to close and crimp edges to seal; place on grill; close lid; cook until packets are fully puffed, 10 minutes.
Combine remaining 1/4 cup cilantro with remaining 1/4 teaspoon salt, mango, avocado, tomato, onion, jalapeño and lime juice in a bowl. Carefully cut foil to open; stir contents; garnish with salsa before serving.