To prepare salsa, combine first 6 ingredients in a medium bowl.
To prepare saté, combine mint, juice, salt, and chili powder in a large bowl; add shrimp, tossing gently to coat. Thread 3 shrimp onto each of 8 (6-inch) skewers. Place shrimp on grill rack coated with cooking spray; grill 1 1/2 minutes on each side or until shrimp turn pink. Serve with salsa. Garnish with cilantro sprigs, if desired.