In a medium bowl, toss the rice with the cilantro and the orange zest. Divide the rice evenly among 4 individual serving bowls. Top with the black beans and half of the pico de gallo. Add warm carnitas and top with the rest of the pico de gallo. Sprinkle on the cheese, and spoon a dollop of the sour cream on top. Finish with the chopped green onions.
In a small bowl, mix 1 teaspoon salt with the pinch of sugar. In a medium bowl, toss the tomatoes gently with the salt mixture. Add onion and jalapeno and combine. Place the avocado on top of the tomato mixture and squeeze with lime juice to coat the avocado. Sprinkle on the cilantro, and stir to combine. Serve.
Rinse and dry the pork shoulder. Salt and pepper liberally. Mix the oregano and the cumin with olive oil and rub all over pork. Place the pork in a slow cooker and top with the onion, garlic, and jalapeno. Squeeze over the juice of the orange and add the two halves. Cover and cook on low for 8 to 10 hours or on high 4 hours. Once the meat is tender, remove from slow cooker and let cool slightly before pulling apart with a fork. In a large saute pan, heat the vegetable oil over high heat. Press the carnitas into the oil and fry until crusty on one side. Serve.