Place 10 4-ounce ramekins in a 9x13 baking pan. Spray ramekins lightly with cooking spray. Place the sugar in a medium saucepan. Stir constantly over medium heat, until the sugar melts and turns the color of honey, about 8-10 minutes. Distribute the caramel among the ramekins, working quickly before the caramel hardens. Sprinkle 1 tablespoon diced mango in each ramekin. Set aside. Preheat oven to 350° degrees. Using an electric mixer, beat mango puree with eggs on low speed to combine. Increase speed to medium high, and mix until incorporated. Add condensed milk, evaporated milk and salt, continuing on medium high for 2-3 minutes. Ladle custard over caramel in the ramekins, filling them to 1/2 inch from the rim. Place filled ramekins in a baking dish and pour enough hot water to reach halfway up the sides of the ramekins. Cover baking dish tightly with foil and place in the oven. Bake until flan is set, about 45 minutes (when you tap the edge of a ramekin the flan should still wobble a little in the center). Carefully remove baking dish from oven, remove foil, and let ramekins cool slightly. Using tongs, remove the ramekins from water and set on a towel to cool for at least two hours before serving. Once it is cooled completely, flan can be refrigerated for up to one day before unmolding and serving. To serve, run a thin knife around the inside edge of the ramekin to loosen flan, and then invert it onto the plate. Add a sprig of mint for garnish.