In a small bowl whisk together the allspice, cinnamon, brown sugar, cumin, salt and pepper. The seasoning mix can be made ahead of time and kept in an airtight container.
For the chicken:
Pat the chicken legs dry with a paper towel. Combine the orange juice, lime juice, soy sauce and olive oil in a small bowl. Pour the juice mixture over the chicken then rub the chicken skin inside and out with the seasoning mix.
Cover and marinate, refrigerated, for at least an hour and up to a day.
Preheat the oven to 400ºF (200ºC). Bring the marinated chicken to room temperature then arrange the chicken in single layer in a 13 x 9 x 2-inch glass baking dish.
Bake until evenly browned and cooked through, about 40 minutes.
Heat broiler to high and broil chicken, watching closely, until the skin is crisp and lightly charred, about 3 minutes.
For the salsa:
In a small mixing bowl stir together the avocado, mango, red onion, lime juice, jalapeño, cilantro and salt until combined.
To serve:
Serve the chicken legs topped with a scoop of mango salsa with a side of white rice and black beans.