Heat a large skillet over medium heat; add ground beef and cook and stir for 5 minutes or until browned.
Reduce heat to low and add next 5 ingredients (garlic through beef broth); simmer for 10 minutes or until most of the liquid has evaporated.
Remove from heat and set aside to cool.
Transfer cooled ground beef to a large bowl; add next 5 ingredients (spinach through avocados).
In a small bowl, whisk together remaining ingredients (vinegar through olive oil); drizzle mixture over the taco salad; toss and serve.