In a blender, pulse the mango, mango nectar, vanilla extract, lemon extract, and salt until chopped up but not completely smooth.
Pour into the bottoms of four 12 to 16-oz glasses. Rinse out the blender.
Add the grapes, avocado, and honeydew melon to the blender and pulse until chopped up, but not completely smooth. Carefully pour the mixture over the mango making your second layer. Rinse the blender.
Repeat with the cantaloupe and watermelon. Pour on top of the grapes, avocado and honeydew layer to create your third layer.
Garnish with a cube of melon, sprig of mint, and slice of avocado.