It is important that the mixture marinate at least overnight in the fridge to allow the vinegar and spices to correctly flavor the meat.Mexican oregano can usually be found in all grocery stores and usually will be in the section where the spices (dried chile peppers etc.) are in bags and hanging on hooks, don't substitute until you have exhausted your efforts.
I usually fry loosely until browned and then add eggs and serve in warm tortillas.
Add a little Ranch dressing and Cheddar cheese and you are in breakfast heaven. OR OR OR eat the chorizo by itself, it is sooo good and you know WHAT is in there. Read the ingredient list on store bought chorizo and it will blow your mind. Kinda gross actually. Now you can enjoy chorizo with peace of mind.