DO-AHEAD TIP: If using bamboo skewers, presoak them in water for 30 minutes, to prevent burning on the grill.
Preheat grill to MEDIUM.
In a large zipper-topped plastic bag, combine first 6 ingredients (salt through lime juice); add shrimp, seal bag and toss well to coat; set aside.
In a small bowl, combine next 6 ingredients (mango through garlic). Blend well then set aside. Thread shrimp onto skewers. Lightly oil the grill grate then grill shrimp over indirect heat for 1 to 2 minutes per side or just until pink and opaque.
Watch carefully to prevent burning! Serve hot shrimp skewers over chopped spinach, top with mango salsa and enjoy!!