Prepare the marinade: In a small bowl, combine all the marinade ingredients and whisk to combine. Taste for seasoning and adjust if necessary.
Place the chicken breasts between two sheets of plastic wrap and pound to flatten slightly with a rolling pin. Arrange the chicken breasts in a large shallow glass dish and pour the marinade over, Turning to coat evenly. Cover and refrigerate for 2 to 4 hours, turning several times to make sure the marinade covers all the chicken.
Meanwhile prepare the salsa: Place the red pepper in a preheated 425*F oven and roast until skin is well blistered. (alternatively roast over a gas flame) Place blistered pepper into a zip lock baggie and close the bag. Let it sit for about 10 to 15 minutes. Remove from bag. Slip peel off and remove seeds. Chop roasted pepper and combine with remaining salsa ingredients. Mix well, cover and chill until ready to serve.
Prepare a charcoal or gas grill for medium high heat grilling. Remove the chicken from the marinade and place on grill rack. Grill, turning once for 7 to 10 minutes on each side, or until juices run clear. Alternatively, you may broil the breasts for 7 to 10 minutes on each side, once again, until the juices run clear.
To serve, place the chicken on individual plates and spoon the mango salsa on top.