Working over a large bowl, finely grate the zest from the 1/2 orange and then squeeze in about 2 tablespoons of juice. Stir in the 1/4 cup minced onion, the jalapenos, cumin, coriander, garlic powder, 1 1/2 teaspoons salt and 1 teaspoon pepper. Add the pork and mix well. Form the mixture into 4 patties; transfer to a plate or baking sheet.
Preheat a grill, grill pan or large cast-iron skillet over medium-high heat. Cook the patties, turning once or twice, until an instant-read thermometer inserted in the thickest part of a patty registers 160 degrees F, about 10 minutes.
Meanwhile, cut the avocados in half lengthwise and discard the pits. Scoop the flesh into a medium bowl and, using a fork, lightly mash into a chunky paste. Fold in the cilantro, lime juice and the remaining 2 tablespoons red onion; season with salt and pepper.
Transfer the patties to a clean plate or baking sheet and tent with foil; let rest for 5 minutes. On the grill, grill pan or in the skillet, toast the buns over medium-high heat until golden, 1 to 2 minutes. Put the patties on the bottom buns and top with the guacamole. Close the burgers and serve.