Slather the adobo thickly over the pig, inside and out, and marinate, refrigerated, overnight or for at least 4 hours. Remove from the refrigerator 2 hours before roasting and let it come to room temperature while you prepare the remaining ingredients to make the stuffing.
Dice or mince the stuffing ingredients as directed above.
In a large Dutch oven or deep skillet, heat the oil to rippling over medium-high heat. (It may be necessary to divide the work between two skillets or work in 2 batches.) Add the onions and garlic and cook, stirring for 2-3 minutes, until slightly translucent. Add the chopped tomatoes and cook, stirring, for 5 minutes to evaporate the juices slightly. Stir in the remaining ingredients, except for the orange juice; reduce the heat to medium and cook, uncovered, for 15 minutes, stirring often. Let the mixture cool to room temperature.
Preheat the oven to 350°F.
Season the pig generously with salt and pepper, inside and out. Stuff it with the cooled fruit and vegetable mixture and close the opening with skewers.
If not using the optional orange juice, arrange the pig in a large roasting pan so that it is lying on all fours and roast for approximately 3 hours, or until a meat thermometer inserted in the thigh reads 160°F. Reduce the heat to 200°F and let the pig rest at this temperature for 15 minutes or until ready to serve (but no longer than 40 minutes). Otherwise lay the pig on one side and pour the orange juice over it. Roast as directed but baste occasionally with the juice and turn the pig onto the other side halfway through cooking. If the liquid seems to be evaporating too fast, add small amounts of water (not more than ¼ cup at a time) to the pan juices.
Carve the pig. Arrange the stuffing on a serving platter with the carved meat on top. If enough orange juice is left to serve as gravy, strain it and skim off the fat; pass separately in a gravy bowl.