In a very large bowl, combine garbanzo beans, tomatoes, cucumber, green pepper, cilantro and onion; set aside.
For dressing, in a screw-top jar, combine oil, vinegar, salt, garlic and sugar. Cover and shake well. Season to taste with additional sugar, if desired. Pour dressing over vegetable mixture, tossing to coat. Sprinkle over the top the feta cheese, if desired. Cover and chill 4 to 24 hours.
Let stand at room temperature for about 15 minutes before serving. Serve alone or toss with mixed greens as a light entree. If desired, serve lemon wedges to squeeze over salad. Makes 8 to 10 side-dish servings.