In a medium bowl, whisk the orange juice, lime juice, oil, sugar, ancho powder, garlic, pepper flakes, and 1/2 tsp. salt.

Add the pork, toss to coat, cover, and refrigerate for at least 1 hour or up to 4 hours.

Thread the pork and mango cubes onto the skewers, alternating them and beginning and ending with a piece of pork. Each skewer should have about 5 pieces of pork and 4 pieces of mango.

Prepare a medium gas or charcoal grill fire. Scrub the grill grate with a wire brush and then wipe clean with a paper towel dipped in oil. Cook the skewers, turning once, until the meat is browned on the outside but still slightly pink in the center, about 8 minutes. Serve garnished with the cilantro.