Mix tomatoes, onion, cilantro, jalapeno peppers, 1 tablespoon juice from jalapeno peppers, and garlic salt in a bowl; squeeze 1/2 lime over salsa fresca. Cover bowl with plastic wrap and refrigerate while preparing fish.
Toss coleslaw mix with ranch dressing in a bowl; set aside for flavors to blend.
Heat oil in a deep-fryer or large saucepan to 350 degrees F (175 degrees C).
Stir batter mix and beer together in a bowl. Wrap corn tortillas in wet paper towels and set aside.
Dip cod in the batter mix; fry coated cod in batches in the hot oil until cod is cooked through and coating is brown, 4 to 5 minutes. Remove cod with a slotted spoon and drain on a paper towel-lined plate.
Microwave corn tortillas on high until warmed, about 1 minute.
Stack two tortillas on a plate; top with fish, a sprinkle of Mexican cheese, coleslaw mixture, salsa fresca, and a squeeze from lime wedge. Drizzle with chile-garlic sauce. Repeat with remaining ingredients.