Place first 6 ingredients in processor until almost smooth. Add juice and blend well. Season spice mixture with salt pepper. Sprinkle fish with salt and pepper. Rub the spice mixture over each fillet. Refrigerate 2 hours.
Preheat grill. Remove fish from marinade and season with salt and pepper. Grill for 3 minutes on each side.
Whisk together the ingredients and season with salt and pepper to taste.
Place greens in a large bowl and drizzle with some of the dressing, season with salt and pepper and toss to coat, divide among 8 plates.
Arrange grapefruit segments and mangoes atop greens and drizzle with some of the dressing; place 1 fish fillet along each salad. Top fish with avocado.