Cut or peel the rinds from the grapefruit and orange, making sure to remove the white pith, which is bitter. Slice crosswise into 1/ 4=inch rounds. Cut each round into large bite-sized pieces. Transfer toa large salad bowl.
Cut the avocados in half lengthwise and carefully(!) remove the pit. Cut into lengthwise quarters then slice across each quarter into 1/ 2-inch pieces. Add to the salad bowl.
Slice the Persian cucumber crosswise into 1/8-inch slices. Add to the salad bowl.
Use a fork or small tongs and remove the red onion slices from the dressing. Add to the salad bowl.
Add about one-half of the dressing then gently toss the salad ingredients taking care to not mush the avocado slices and break apart the citrus slices. Lastly add the cilantro and give the salad a final stir. Add additional dressing if needed, taking care to not overdo it.
Spread the salad greens onto a wide, shallow serving bowl or plate. Drizzle a bit of remaining dressing onto the greens and lightly toss. Arrange the avocado, citrus and cucumber mix atop the salad greens. Serve immediately.