Combine 2 tablespoons juice, onion, and next 5 ingredients (through salmon), stirring well. Combine cheeses. Divide half of cheese mixture evenly among 3 tortillas. Top each tortilla with about 1 1/3 cups bean mixture. Sprinkle evenly with remaining cheese. Top with remaining 3 tortillas.
Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Place 1 quesadilla in pan; cook 4 minutes on each side or until golden. Remove and keep warm. Wipe skillet clean with paper towels. Repeat procedure with remaining cooking spray and quesadillas. Cut each quesadilla in half; cut each half into 3 wedges.
Combine remaining 1 tablespoon juice, tomatoes, avocado, sour cream, and salt; toss gently. Serve with quesadillas. Garnish with cilantro sprigs and lime wedges, if desired.