Toast the shredded coconut in a small, dry skillet over medium-high heat for 3 to 4 minutes, tossing often, until most of it turns a rich, soft brown. Turn out onto a saucer to cool.
In a medium bowl, combine the lime juice, fish sauce, and sugar and stir well to dissolve sugar and form a smooth sauce. Add the pomelo, toasted coconut, dried shrimp (if using), shallots, chilies, and mint, and toss gently to combine everything well.
Transfer to a serving platter with lettuce leaves on the side, and serve at room temperature.