In 2-quart saucepan over medium heat, cook water, sugar, and lime juice 15 minutes or until mixture becomes a light syrup. Stir in mint leaves; cover and refrigerate until well chilled.
Cut watermelon into bited-sizepieces; discard seeds. Cut cantaloupe into bite-sized pieces; cut unpeeled plums and nectarines into wedges. Combine cut-up fruits with grapes and arrange in very large bowl. Pour chilled syrup through strainer over fruit; gently toss to mix well. Cover and refrigerate to blend flavors, stirring mixture occasionally.