1. Prepare grill or broiler, or have a ridged grill pan ready to preheat. Combine shrimp and bell pepper chunks in a medium bowl. Add fish rub or Cajun seasoning; toss to coat lightly. Thread shrimp and bell pepper (alternately) on metal or bamboo skewers (the latter presoaked in water); coat with cooking spray.
2. Arrange lettuce, avocado, and mango on 4 large plates. Combine salsa, chutney, and lime juice; mix well. (Salads and dressing can be prepared up to 2 hours before serving; chill separately.)
3. Put shrimp skewers on medium-hot grill, under broiler 4 inches from heat, or in grill pan over medium-high heat. Cook 3-4 minutes per side or until shrimp are opaque. Remove shrimp and peppers from skewers; arrange over salads. Drizzle salsa mixture over salads; top with cilantro, if desired.