For this dish you want an avocado that is slightly under ripe to perfectly ripe. This will give you an avocado that is delicious and creamy but has a slightly firm texture so you can fold it into the salad without mashing it. To pick the right avocado you should go by feel. When you gently press on the avocado it will feel slightly soft but not mushy. As long as it has just a small amount of give but still feels firm you've got the perfect avocado. Make sure you use it within 1-2 days. Avocados are notorious for going over ripe in the blink of an eye!