Cut one orange in half; squeeze juice from one half to measure about 3 tablespoons. For dressing, combine juice, olive oil and 1 teaspoon jerk seasoning in small bowl. Mix well; set aside.
Rub beef steak on both sides with remaining jerk seasoning.
Place steak on grid over medium, ash-covered coals; grill steak, covered, 10 to 14 minutes (over medium heat on preheated gas grill, covered, 10 to 14 minutes) for medium rare (145°F) to medium (160°F) doneness, turning occasionally. Carve steak diagonally into thin slices.
Meanwhile, peel remaining orange and orange half; cut into sections. Place in medium bowl with arugula and avocado. Add dressing; toss gently.
Stack two tortillas for each taco. Top one side of tortillas with beef slices, arugula-avocado mixture and cashews; fold in half. Serve immediately.
Nutrition information per serving: 635 Calories; 252 kcal Calories from fat; 28 g Total Fat; 5 g Saturated Fat; 15 g Monounsaturated Fat; 66 mg Cholesterol; 355 mg Sodium; 68 g Total Carbohydrate; 12.8 g Dietary Fiber; 31 g Protein; 2.7 mg Iron; 8 mg NE Niacin; 0.7 mg Vitamin B6; 1.2 mcg Vitamin B12; 5.2 mg Zinc; 29.2 mcg Selenium; 110 mg Choline;