Cut mango, cucumbers and avocado, and set them in a bowls in an assembly line. Wash and dry lettuce or chard, tearing it into smaller leaves if needed. You can fill the leaves with the shrimp, mango, cucumber and avocado mixture and stop here if desired. If using the rice paper wrappers, fill a 9 x 13 pan with water. Dip each wrapper in the pan for a second and lay on a paper towel to dry. If the wrappers are circular, fold in the left and right sides just until they touch. Layer lettuce, shrimp, avocado, mango and cucumber, then roll the roll rice wrapper up until it seals at the top. Voila!