Okay, I'm a two-time graduate of the Defense Language Institute.
I need more information to help you figure this out, though.
What service are you joining? The services have their own criteria.
What specialty (MOS) are you going into? There are differences in the approach for language training depending on the MOS you will be training into.
As a for instance - in the US Army, a 98G Voice Intercept Operator will attend language training first, then upon completion of language training, will report to their AIT for technical training. Add 8-10 weeks for basic training and you won't see your first line unit for anywhere from 14 months to 2 years.
a 97E Interrogator will do AIT first, then go to Language School. Again, a good long time between reporting for basic training, completing all of your training, and getting to your first line unit.
Good luck. As a linguist, you will always have at least one trade you can market after you finish your military training.