1. Partially freeze pork; thinly slice across grain into bite-size strips. Place pork in a plastic bag set into a bowl. Combine salsa, lime juice, beer, garlic, cilantro, cumin, and red and black peppers. Pour over pork; seal bag. Marinate in refrigerator 3 to 4 hours. Prepare Guacamole; chill.
2. Wrap tortillas in foil. Heat in a 350 oven for 10 minutes to soften. For rice, drain pork and set aside; reserve marinade. Add enough water to marinade to equal 1-1/2 cups. In a saucepan bring marinade mixture to boiling. Add rice. Remove from heat. Let stand, covered, 5 minutes.
3. Meanwhile, spray a 10-inch skillet with nonstick cooking spray; preheat over medium heat. Add half of the pork to skillet. Stir-fry 4 minutes or till no longer pink. Remove from skillet using a slotted spoon; drain liquid if necessary. Repeat with remaining pork.
4. To serve, fill tortillas with pork and Guacamole. Top with yogurt or sour cream and sliced "green onion," if desired. Roll up. Serve with hot rice. Makes 6 servings.