Place pork in large, resealable plastic bag. Add 1 cup orange juice, 1/2 cup lime juice, and the vinegar; close bag to seal. Turn bag to evenly coat pork with marinade. Marinate in refrigerator for 30 minutes, turning bag occasionally.
Meanwhile, in small mixing bowl add and combine all dry spices.
Lightly oil cold grill rack; preheat gas grill to medium-high. Remove pork from marinade; discard marinade in bag. Sprinkle and rub both sides of chops with spice mixture.
Grill chops, uncovered, over direct heat for 12-16 minutes or until internal temperature of pork reaches 145 degrees F., turning chops over halfway during grilling. Transfer chops to cutting board. Loosely cover with foil; let rest for 5 minutes.
Meanwhile, in a medium sauté pan, over medium heat, heat olive oil, add onions and sauté for 2 minutes; then add garlic, continue to cook about 1 minute more or until garlic begins to brown. Remove sauté pan from heat. Add remaining 1/4 cup orange juice, 1/4 cup lime juice, and the white wine. Bring to boil; reduce heat. Simmer, uncovered, until liquid is reduce to half of the amount.
To serve, pour sauce over chops. Garnish with watercress, tomato and avocado.