Make Pickled Onions: In medium saucepan over medium-high heat, bring to simmer water, vinegar, sugar and Adobo. Stir in onions. Transfer onion mixture to bowl or glass jar until cool. Cover and store in refrigerator up to 3 days.
Marinate Pork and Pineapples: In plastic zip-top bag, combine 1 cup Mojo Piña, pork and 3 tablespoons olive oil. Seal bag, massage to coat pork in marinade and transfer to refrigerator for at least 2 hours, and up to 24 hours. In separate zip-top bag, combine pineapple with remaining 2 tablespoons Mojo and remaining 1 tablespoon oil. Seal bag, massage to coat and marinate 15 minutes. Remove pork and pineapples from marinade, discarding marinade.
Grill Pork, Pineapple and Poblano: Heat grill to medium-high heat. Add pork, pineapples and poblano peppers to hot grill grates. Grill pork, flipping once, until just pink in center (145°F on instant-read thermometer), about 6 minutes. Grill poblanos and pineapple until just tender, about 6-8 minutes; transfer to plate.
Assemble Tortas: Scoop out some of soft bread from roll tops. Layer bottom rolls with poblano, pork, pineapple, avocado and cheese. Top with jalapeños, cilantro and reserved pickled red onions to taste.