1. Preheat grill to medium-high heat.
2. Combine chopped cilantro, 1 tablespoon sugar, and next 4 ingredients (through soy sauce) in a large zip-top plastic bag. Add beef; let stand 15 minutes. Remove beef from marinade; reserve marinade.
3. Place beef on grill rack coated with cooking spray. Drizzle with reserved marinade. Grill 5 minutes on each side or until desired degree of doneness. Remove from grill; cover with foil. Let stand 5 minutes; cut across grain into thin slices.
4. Combine lime juice, 2 tablespoons water, peanut butter, remaining 2 teaspoons sugar, and pepper in a large bowl; stir with a whisk. Add lettuce and next 4 ingredients; toss to coat. Divide salad evenly among 4 plates; top evenly with mango. Serve with beef.