Joining the Navy will give you great experience. You should consider taking some college classes while in the Navy. You can take classes online.
If criminal justice is not listed as an option when selecting a degree or occupation, try to find something similar (criminology, police technology, administration of justice, law enforcement, etc.). If you can't, you can certainly select "undecided". Be sure to take advantage of the Act test prep guides, practice tests, and test tips. They can really help!
I am not familiar with colleges in New Mexico, but you might want to consider the University of New Mexico. They offer a four year degree in criminology that looks good. National American University is another school that you could consider. They offer a four year degree in criminal justice.
Good luck! Keep us posted.