In a large frying pan, cook sausage until there is no pink and cooked thoroughly. Drain grease and add sausage to a medium oven safe bowl. Place in 170° oven to keep warm.
In another frying pan, add about 1/4" of oil in bottom of pan. Heat over medium flame and once oil is hot, gently place potatoes and onions into pan. Sprinkle with garlic salt and pepper. Cook until potatoes are done and golden brown.
Fry up the corn tortillas and place on a plate lined with paper towels and place in the oven until ready to fill.
In the frying pan the sausage was cooked in, add eggs and scramble until done.
To assemble the breakfast tacos, add a spoonful of potatoes in the bottom of the tortilla, followed by sausage, Jack cheese, scrambled eggs, Pepper Jack cheese then top with sour cream, avocados and tomatoes.