1. Preheat broiler to high.
2. Arrange corn in a single layer on a heavy-duty baking sheet; broil 6 minutes or until lightly browned, stirring once.
3. Arrange crackers in a single layer on a baking sheet; top evenly with cheddar and Monterey Jack cheeses. Broil 3 minutes or until cheese is bubbly and crackers are lightly toasted. Divide crackers evenly among 4 plates. Combine salsa, cream cheese, and beans in a food processor. Add 1/4 teaspoon salt to salsa mixture; pulse until mixture is chunky and well blended.
4. Arrange 1/2 cup lettuce over each serving, and top each with about 6 tablespoons bean mixture, 1/4 cup corn, 1/4 cup tomato, and 1/4 cup avocado. Sprinkle evenly with remaining 1/4 teaspoon salt.