Is it a good idea to get an associate's degree in criminal justice?

It depends on your overall career goals and objectives. An associates degree is a great way to start. However, I would seriously consider transfer to a four year institution after completion of the associates degree to pursue your bachelors degree. It will open up more doors of opportunity for you. Acquire a vision of exactly what it is that you want to accomplish in terms of career goals, and your path will become clear.