Put garbanzo beans in colander and rinse very well until no more foam appears. Remove any chickpea skins that come off when you're rinsing the beans. Let beans drain at least 15 minutes. (I sometimes pat them dry with a paper towel if I'm in a hurry and they seem quite wet.) Mix olive oil and balsamic vinegar with a whisk. Place beans in small ziploc bag, pour dressing over and marinate beans in refrigerator 4-6 hours or longer.
When you're ready to prepare the salad, remove beans from refrigerator and drain them in a colander, reserving the dressing. Taste dressing for seasoning, and if you don't have at least 3 T dressing, add a bit more balsamic vinegar and olive oil.
Dice tomatoes and if they're extra juicy, put in colander to drain while you prepare other ingredients. Cut cucumbers into fourths lengthwise, and then into pieces about 1/2 inch wide. (If cucumbers seem wet, pat dry with paper towel.) Wash oregano, spin dry or dry with paper towel, and coarsely chop using a chef's knife.
Combine tomatoes, cucumbers, garbanzo beans and oregano and toss with reserved salad dressing. Season salad with salt and fresh ground black pepper to taste. Divide salad among individual serving plates, and top with crumbled Feta or Goat cheese just before serving.