Combine the shrimp with the orange juice, chipotle pepper, and garlic. Marinate for 15 minutes. Heat the oil in a large cast-iron skillet or sauté pan over medium-high heat. When the oil is lightly smoking, add the onion and pepper and cook for about 10 minutes, until lightly charred on the outside. Push the vegetables to the perimeter of the pan and add the shrimp to the center. Sauté until cooked through, about 10 minutes. Season with salt and pepper to taste. Remove from the heat. Coat a separate nonstick pan with cooking spray, oil, or butter and heat over medium-low heat. Place one tortilla in the bottom, sprinkle with half of the cheese, then top with half of the shrimp mixture and a second tortilla. Cook for about 5 minutes, until the bottom is very crisp, then flip and cook for another 2 to 3 minutes. Cut the quesadillas into wedges and serve with salsa and a bit of guacamole, if you like.