Place pork and juices in a 2-quart square microwave-safe baking dish. Cover loosely and microwave on 100 percent (high) for 2 minutes. Shred pork using two forks to pull through meat in opposite directions. Drain pork and return to baking dish. Stir in salsa. Cover loosely and microwave on high 2 minutes more or until hot. Keep warm.
To warm taco shells, place on a baking sheet and heat according to package directions. (Or, to warm flour tortillas, wrap tortillas tightly in foil. Heat in a 350 degree F oven about 10 minutes or until heated through.)
To assemble tacos, place pork mixture in warm taco shells. Top with lettuce, cheese, and olives. (If using flour tortillas, place pork mixture in center of warm tortillas and add remaining ingredients; fold tortillas in half.) If desired, serve with sour cream and avocado.