1. For the marinade: Pulse the chipotles and adobo sauce, orange juice, cider vinegar, dark brown sugar, oil and 1/2 teaspoon salt in a mini-food processor or blender until smooth and emulsified. Reserve 1/3 cup of the marinade and set aside. Place the chicken and steak in separate large resealable plastic bags, divide the remaining marinade between the bags and toss the meats to coat. Seal the bags and refrigerate for 1 hour.
2. For the corn salsa: Prepare a grill for medium-high heat. Lightly oil the grill grates. Brush the corn cobs evenly with 2 tablespoons vegetable oil and sprinkle ears with 1/2 teaspoon salt and a few grinds of pepper. Grill, turning occasionally, until the kernels are cooked through and charred in spots, 10 to 15 minutes. Set aside to cool slightly; keep the grill heat at medium-high.
3. Whisk the mayonnaise, lime zest, lime juice, and Parmesan in a large bowl until combined. Cut off the corn kernels with a paring knife and stir into the mayonnaise mixture. Mix in the coriander and set aside.
4. For the taco bar: Transfer the chicken and steak to a rimmed baking sheet and sprinkle with 1 teaspoon salt . Wrap the tortillas in foil and set to the side on the heated grill to warm while you cook the meat.
5. Arrange the chicken and steak on the grill, brush the tops with some of the reserved marinade and cook 5 minutes. Flip, and cook until the chicken is cooked through and the steak is medium-rare, another 5 minutes for thinner pieces, and 7 to 8 for thicker. Right before you take the chicken and steak off the grill, brush with the reserved marinade, flip, and cook to caramelize the marinade, about 1 more minute. Transfer the chicken and steak to a cutting board and let rest 5 minutes before slicing. Roughly chop the chicken into 1-inch chunks and slice the steak across the grain. Serve immediately with the tortillas, corn salsa, Monterey Jack, avocados, limes, radishes and salsa.