Place ribs, salt, pepper, garlic, paprika, and chipotle pepper (if using) into a crockpot. Cover with orange juice, orange zest and water and cook on low for 6 hours. Shred meat with forks and allow it to continue warming.
To make sauce: combine cilantro, garlic, jalapeno, lime juice olive oil and Greek yogurt in a blender or food processor and pulse until smooth. Sauce should be able to be drizzled. If it is too thick, add water and mix again.
To make taco shells: break leaves off the bunch of curly leaf lettuce and use a large knife to break the steam. Fill each taco with about 1-2 ounces of pork, peppers, 1 tbsp. of yogurt and 1 tsp. of the green sauce.