Google Voice services are still only being offered by invite only. I personally requested an invite and it took nearly 3 weeks for my profile to be accepted by Google. Now the Mountain View, California company is approving military personnel profiles at a much faster and guaranteed rate.
According to the Google Voice Military Services page, Military personnel will receive acceptance into the program within one to two days. Here's there only requirment:
Please leave your .mil email address (so we know you are in the military), and we'll send you a Google Voice invite within a day or two.