1. Prepare grill to medium-high heat.
2. Brush 1 1/2 teaspoons soy sauce over cut sides of figs. Place figs, cut side down, on a grill rack; grill 1 minute on each side or until lightly browned. Remove from grill.
3. Combine remaining 1 tablespoon soy sauce, juice, honey, oil, garlic, and salt; stir with a whisk.
4. Combine arugula, spinach, celery, onion, and pepper. Arrange 2 cantaloupe wedges on each of 6 plates. Top each serving with about 1 cup arugula mixture, 3 fig halves, and 1 1/2 teaspoons nuts; drizzle with about 1 1/2 tablespoons dressing.