Heat the oven to 200 F.
In a food processor, combine the avocado, buttermilk, 1 clove of garlic, lime juice and salt and pepper. Puree until smooth, then set aside.
In a medium bowl, combine the cabbage, remaining garlic, carrot, radishes, vinegar, sugar, lime zest and hot sauce. Season with salt and pepper and toss well. Set aside.
Heat a heavy skillet (such as cast-iron or stainless steel, but not nonstick) over medium heat. One at a time, place the tortillas in the skillet and toast for about 30 seconds per side. As the tortillas are toasted, stack them on a sheet of foil. Wrap the foil around the tortillas, then place them in the over to keep warm. Alternatively, the tortillas can be held with tongs and toasted directly over a gas burner for a few seconds per side.
In a pie plate or other wide, shallow bowl, combine about 1 cup of flour with 1 tablespoon of salt and 1 teaspoon of pepper. One at a time, dredge each piece of fish through the flour until coated evenly. Shake off any excess.
In a large nonstick skillet over medium-high, heat about 1 tablespoon of the oil over medium-high. Add half of the fish to the pan and cook, turning once, until golden and cooked through, about 3 minutes a side. Transfer to an oven-safe plate and set in the oven to keep warm. Repeat with the remaining oil and fish.
To serve, top each tortilla with a bit of the avocado puree, then a piece of fish. Drain the cabbage mixture, then mound some of that over each portion. Serve with jalapeno slices and cilantro on the side.
Nutrition information per serving: 500 calories; 190 calories from fat (38 percent of total calories); 22 g fat (3 g saturated; 0 g trans fats); 60 mg cholesterol; 51 g carbohydrate; 10 g fiber; 5 g sugar; 31 g protein; 370 mg sodium.