Combine 3 tablespoons balsamic and EVOO in bowl and whisk to emulsify.
Place fillets in a shallow glass dish or resealable plastic bag. Pour marinade over the fish and turn fillets to coat. Let marinate for 1 hour, turning occasionally.
Heat grill on high heat.
While the grill is heating, combine coleslaw mix, mayonnaise, 2 tablespoons balsamic, cilantro, and salt blend in a bowl. Set aside.
Cut baguettes into 5 portions and slice each horizontally. Remove fillets from marinade and season on both sides with salt and pepper.
Grill fish to desired doneness. Serve on baguette with spicy slaw and sliced tomatoes.