Rinse fish; pat dry. Measure thickness of fish; set aside. In a small bowl stir together cilantro, oregano, lime peel, lime juice, oil, pepper sauce, and garlic. Place 2 tablespoons cilantro mixture in a medium bowl. Add beans and avocado; toss lightly to coat. Cover and refrigerate while cooking fish.
Brush remaining cilantro mixture over fish. Grill fish on the lightly greased rack of an uncovered grill directly over medium heat until fish flakes easily when tested with a fork, turning once. (Allow 4 to 6 minutes per 1/2-inch thickness of fish.) Serve with bean mixture. Makes 4 servings.