Combine all Marinade ingredients in a small bowl. Rub both sides of fish fillets with the marinade and place in a glass baking dish. Cover and refrigerate for 30 minutes to 3 hours.
For the Southwest Sauce
Using a medium bowl, add all of the Southwest Sauce ingredients; whisk together until well blended. Set aside.
For the Tacos
Preheat grill to medium-high heat.
Brush grill grates with vegetable or canola oil to prevent fish from sticking.
Grill fish 3-4 minutes per side, or until fully cooked. (Tip: When fully cooked, fish should flake easily with a fork.) Transfer fish to a large plate or cutting board; let rest for 5 minutes.
Meanwhile, place the tortillas on the grill for 25-30 seconds, or until soft and pliable.
Using 2 forks, flake the fish into bite-sized pieces and place in a bowl. Whisk together the lime juice and olive oil; drizzle this mixture over the flaked fish.
Divide the fish into the tortillas and top with cabbage, avocado, cilantro, red onion and southwest sauce.