Cook the pasta as per the package instructions, adding salt to the boiling water. A minute before the pasta is done, add the broccoli to blanch. Drain and rinse under cold water to stop the cooking process.
In a large bowl, whisk together the mayonnaise, vinegar, salt, pepper, and sugar until smooth.
Add the cooled pasta and broccoli to the dressing and mix well. Fold in the cucumber, red bell pepper, black olives, and green onions until everything is evenly coated.
Cover the bowl and refrigerate the salad to let the flavors meld. Give it a good stir before serving to redistribute the dressing.