Remove the chorizo from the casing, break up and fry until crumbly. Remove with a slotted spoon, and set aside. Drain all of the grease except two tablespoons. Add the onions and potatos and fry until the onions are soft and the potatoes are slighty browned. add the chorizo back in the skillet along with the eggs and scramble until the eggs are set. Serve with tortillas and top with cheese and salsa.