In a large bowl, toss the pork with the garlic, chili powder, salt, pepper and cumin. Let stand for 5 minutes. Thinly slice half of the onion, add it to the bowl with the vinegar and any reserved pineapple juice and toss with the pork. Marinate for 1 hour at room temperature (or slightly longer in the refrigerator). If chilled, bring to room temperature before grilling.
Preheat the grill or broiler. Thread pork and pineapple chunks alternately onto 8 skewers. Discard the marinade. Grill the kebobs or broil 4-inches from heat for 2 minutes per side. (8 minutes total), or until the pork is no longer pink in the center. Transfer to a platter.
While the pork is cooking, finely chop the remaining half of the onion. Place onions, cabbage, cilantro and salsa into individual serving bowls. Place all of the tortillas in a paper towel that has been sprinkles with a few tablespoons of water. Heat on half-heat for about 2½ minutes in the microwave. See Notes below if you'd like to deep-fry the tortillas instead. Keep wrapped and place in basket. Serve tacos immediately with fixings.
Notes
If you are preparing this recipe as GLUTEN FREE, just be sure to use a brand of corn tortillas that is known to be GF.