Combine garlic, cumin, chili powder, vinegar, molasses, and orange and lime juices in a small saucepan; bring to a boil over high heat. Boil for 2 minutes, remove from heat, and set aside. Halve lemons crosswise, and cut each half into 4 wedges.
On each of six long metal skewers, arrange 4 lemon wedges, 3 bay leaves, 3 pieces of fish, and 2 tomatoes. Kabobs can be prepared up to this point and refrigerated for up to 6 hours before cooking.
Heat grill to medium hot. Sprinkle kabobs with the salt and pepper, and spoon glaze over them. Grill until fish is opaque to the center and lightly charred, 3 to 4 minutes per side; brush with glaze several times while cooking. Remove skewers, and serve.
Soak the wooden skewers in water for at least 20 minutes before using to prevent charringduring cooking.