In small bowl, combine Sazón, garlic, cilantro, olive oil, Adobo, oregano, cumin and hot pepper flakes until well combined.
Pat chicken dry with paper towels. Rub spice mixture all over chicken; transfer to non-reactive container or large zip-top bag. Cover and refrigerate for at least 4 hours, or up to 48 hours. Bring chicken to room temperature 30 minutes before grilling.
Heat grill to medium-high heat. Place chicken skin-side down over direct heat. Cook until skin is dark golden brown and crisp, 15-17 minutes. Carefully flip chicken; transfer to area of grill over indirect heat. Grill until chicken is cooked through (instant-read thermometer registers 165°F when inserted into thigh without touching bone), about 45 minutes more. Transfer chicken to platter. Let rest 15-30 minutes. Carve and serve.