Forget the "little time off" idea and working in August. Even if you enlist tomorrow as a reservist or National Guardsman, you would attend basic training, followed by some sort of technical or other schooling. Figure on about six months before you could be screened, enlisted, trained and released back to your unit.
If you are interested in being in an elite unit, best find an Army Reserve or National Guard organization with a special mission. This would allow you to attend Airborne training, and with the investment of a few more months, possibly Ranger training. From screening to completion, figure on six to ten months.
For even quicker completion, join the Marine Corps Reserve and find an infantry unit where you will not have lengthy training after boot camp. Even so, figure on a month or two for screening and enlistment and then six months of boot camp and infantry training.
Navy SEALS do not enter that program right off of the street, or even quickly from the ranks of the Navy. Same for Army Special Forces. There are minimum time served requirements, followed by rigorous screening before being considered for training.
See a couple of recruiters. They will fill you in, answer your questions and give you reasonable expectations that the service and you can meet.