Place all ingredients, except avocado and cheese, in a large bowl; toss until evenly mixed.
Just before serving, add vegan cheese and avocado, if desired, stirring gently to mix. Garnish with additional cilantro leaves. Serve with tortilla chips.
Test Kitchen Tip: Nopales are the tear-shaped leaves of the Opuntia or prickly pear cactus, harvested all year long in warm, dry regions of Mexico. The pads are harvested young and have a delicate, tart flavor and crisp yet slightly chewy texture. The juicy leaves are eaten both raw or cooked in a variety of Mexican dishes. Nopales are generally sold fresh in Mexico, but jarred nopalitos can be found in Latin markets, online retailers and in the Latin aisle of most supermarkets.