In a bowl, combine tomatoes, cilantro, poblano, celery, red onion, jalapeno, salt and sugar.
Cook shrimp in boiling water for 40 seconds. Add squid; cook just until seafood is opaque, about 20 seconds longer. Drain and cool; add seafood to tomato mixture.
Tomato Chips: Brush a baking sheet with vegetable oil. Using a mandoline, cut 1 medium tomato in paper-thin slices. Arrange in a single layer on a sheet pan. Brush slices lightly with vegetable oil; lightly sprinkle with salt. Bake at 200ºF until crisp, about 3 hours.
Yuca Chips: Using a mandoline, cut a peeled, 5 oz. piece of yucca in paper-thin slices. In a skillet, over high heat, heat 2 cups vegetable oil. Add half of the yucca slices; fry 2 minutes, turning once; drain on paper towels and cool. Repeat with remaining yucca. Fry chips a second time until brown, about 15 seconds.
To Plate: Spoon seafood-tomato mixture into coconut halves or into lettuce cups, dividing evenly. Garnish with Tomato Chips and Yuca Chips.