Check the package of quinoa, and see if you need to rinse it or not. If not, then skip the rinsing.
Place quinoa in a 1 1/2 or 2 quart sized saucepan, and add the water. Add a half a teaspoon of salt and bring it to a boil. Reduce to a simmer, and cover and cook for about 15 minutes, or until the quinoa is cooked. Then remove from heat.
Let the quinoa cool to room temperature. Spread it out on a sheet pan to quicken the process.
Take the cucumbers and cut them in half in the middle. Then cut each half lengthwise into quarters. Try to scoop out most of the seeds and discard them. Cut the cucumber pieces again, this time crosswise.
When the quinoa is cooled, place it in a large bowl gently with the cucumber chunks, mint, and green onion. You can now sprinkle it with seasoned rice vinegar and toss it again. Sprinkle it with olive oil and gently toss. Add more salt or seasoned rice vinegar. Gently fold in chopped avocado, which is optional.