In a large bowl, combine all liquids and spices. Cut pork into 1/2 inch slices. Place pork into marinade and turn to coat. Refrigerate for at least 4 hours, or up to 2 days.
Cut skin off pineapple, and slice into 2 large chunks (see pictures). Place one piece at the bottom of a large skewer. Skewer all of the pork slices tightly, and finish with other large chunk.
To grill: Preheat grill to medium- high heat. Place skewer on grate, close lid, and cook for 1.5-2 hours, rotating meat once. Cook until internal temperature is 14Allow meat to rest for 5-10 minutes before slicing.
To bake: Preheat oven to 350. Line a rimmed baking sheet with aluminum foil, and place skewer on top. Bake for 1.5-2 hours, until internal temperature is 140. Allow meat to rest for 5-10 minutes before slicing.
To smoke: Set smoker to 350. Place skewer on grate, close lid, and cook for 1.5-2 hours, rotating meat once. Cook until internal temperature is 140. Allow meat to rest for 5-10 minutes before slicing.
After allowing meat to rest, use tongs and a sharp knife to slice thin pieces of meat and pineapple from the skewer.
To serve: Heat 1/2 inch of oil in a deep skillet. Fry corn tortillas for 15-30 seconds on each side, until beginning to crisp. Fill tortillas with meat, pineapple, cilantro, lime juice, diced avocado, and salsa.