Grill peppers and onions over high heat until peppers are well charred and onion is lightly charred. Place peppers in paper bag and fold top over several times; set aside for 20 minutes. Remove peels from peppers by rubbing gently with fingers. Make a slit the length of each pepper and carefully remove seeds and membranes. Place 2 large mango slices and 2 cheese strips inside each pepper. Place on large piece of heavy duty foil and grill over medium heat for 5 to 10 minutes, or until cheese is melted. Remove from grill and keep warm. Chop 1/2 cup mango. Puree grilled onions, remaining mango, lime juice, chipotle peppers and adobo sauce until smooth. Season to taste with salt and stir in chopped mango. Place small amount of mango salsa on each serving plate and top each relleno with additional salsa and snipped cilantro.