Fire up the grill to a medium-high heat. In a small bowl, mix together seasonings (minus adobo seasoning.) Sprinkle over chicken breasts and massage into meat. Place on the grill and cook 5-7 minutes on each side, or until cooked through with a slight char on the edges.
While the chicken is cooking, prepare your tortillas. Spread 1/2 cup cheese onto a tortilla. Top with 1/4 of your sliced avocado, 1-2 tablespoons diced onion, and a sprinkle of cilantro. Sprinkle on a pinch of your adobo spice blend. Repeat with 3 more tortillas.
Place quesadilla on the grill and cook until cheese is melty, flipping halfway through (if your grill bars are wide, you can lay down a piece of foil.) Use a pizza cutter to slice quesadillas into sections.
While quesadillas are cooking, prepare ranch. In a food processor, combine sour cream, half of the cilantro, ranch dip, lime juice, and garlic powder. Pulse until creamy. Pour into a small serving dish and serve with quesadillas.