Remove and discard shrimp tails, if any are present. Coarsely chop shrimp.
In a medium bowl combine shrimp, papaya or mango, mayonnaise, serrano or jalapeno pepper, green onion, lime peel, lime juice, salt, and black pepper. Cover and chill up to 1 hour.
Cut baguette into 4 equal-size rolls. Slice in half lengthwise. Remove some of the bread from the bottom half of each roll, leaving a thick shell. Place rolls, cut side up, on broiler pan or baking sheet; broil 3 to 4 inches from heat for 1 to 2 minutes or until toasted. Place lettuce leaf on bottom of each roll. Spoon shrimp mixture onto lettuce; sprinkle with coconut. Place top half of roll on shrimp mixture. Makes 4 sandwiches.