Spray 3 1/2- to 4-quart slow cooker with cooking spray. Make 1/2-inch-deep slits in pork; stuff with garlic. Place pork in slow cooker. In small bowl, mix cumin, oregano, salt and pepper. Sprinkle mixture on all sides of pork.
In small bowl, stir together orange juice, lime juice and chipotle chiles. Pour mixture over pork.
Cover; cook on Low heat setting 8 hours. Remove pork from slow cooker to large bowl. Shred pork, using 2 forks. Skim fat from cooking liquid. Add 1/2 cup of the cooking liquid to shredded pork; mix well.
Spoon pork mixture evenly onto center of warmed tortillas; top each with 1 1/2 teaspoons onion, 1 1/2 teaspoons salsa and 1 1/2 teaspoons cilantro. Serve with lime wedges.