Combine water and quinoa in a medium saucepan; bring to a boil. Cover, reduce heat, and simmer 20 minutes or until liquid is absorbed. Remove from heat, and fluff with a fork; set aside.
Heat oil in a large nonstick skillet over medium heat. Add jicama and next 5 ingredients (jicama through minced jalapeño pepper); sauté 5 minutes or until tender. Add quinoa, tomato, and next 5 ingredients (tomato through salt); sauté 1 minute or until thoroughly heated. Garnish with small jalapeño, if desired.