1. Place potatoes in a saucepan; cover with water. Bring to a boil. Reduce heat to medium, and simmer 12 minutes or until tender; drain.
2. While potatoes cook, heat a medium skillet over medium-high heat. Add olive oil to pan; swirl to coat. Sprinkle steaks evenly with 1/4 teaspoon salt and 1/4 teaspoon pepper. Add steaks to pan; cook 3 minutes on each side or until desired degree of doneness. Remove steaks from pan; let stand 5 minutes. Cut across the grain into slices.
3. Cook bacon in skillet until crisp; remove bacon from pan, reserving 1 1/2 tablespoons drippings in pan. Crumble bacon, and set aside. Add remaining 1/4 teaspoon salt, remaining 1/8 teaspoon pepper, and flour to pan; cook 30 seconds, stirring constantly. Stir in vinegar, 3 tablespoons water, sugar, and mustard; cook 1 minute or until slightly thickened. Remove from heat; stir in potatoes, steak, bacon, celery, and green onions. Toss with arugula.