Air Force does not use you as a LPN. Your basically a tech. I don't know about Navy. The Army would class you as a LPN, be prepared though to do other jobs though. But, your foundation will be a LPN.
If you go Army there are programs that will help you flip to become an Officer (a BSN Nurse). If you so desire. You would need to do about two years of basic college courses out of way first while your in Army doing your job. It's Called Army Enlisted Commissioning Program.
I am partial to the Army. In the AF you will not use your skills. The army has ways to advance if you actually follow through with a plan. I know a lot of LPNs that have great potential. They talk lot, but never do paperwork and follow through.
But, whatever. Talk to a recruiter, they are not that bad. They actually can be quite helpful. I don't honk they are having a big problem with applicants with the economy the way it is.