Combine olive oil and garlic in a large shallow dish. Add shrimp to dish; toss to coat. Cover, and marinate in refrigerator up to 2 hours; remove shrimp, discarding marinade. Sprinkle shrimp with salt and pepper.
Grill, covered with lid, over medium-high heat (350º to 400º) 2 minutes on each side.
Brush peaches with vegetable oil. Grill, covered with lid, over medium-high heat (350º to 400º) until golden brown. Grill watermelon, covered with lid, just until grill marks form. Cut rind from watermelon. Chop watermelon and cut peaches into wedges; place in a large bowl. Add berries and cilantro; toss gently.
Spoon fruit mixture onto serving plates. Top each serving with 4 shrimp, and drizzle with Honey-Balsamic Dressing. Garnish, if desired.