I am active duty Army and have decided to retire to enable my transition. Believe me when I tell you there are 3 things you must know -
1. AR40-501 (STANDARDS OF MEDICAL FITNESS) specifically prohibits your enlistment (Para 2-27 n. page 15) or retention (Para 3-35, page 33) if you are a cross dresser or transsexual. Download the reg here: http://www.apd.army.mil/pdffiles/r40_501.pdf
2. This is not to say that there are no cross dressers in the military, but if they ask you when you enlist if you are a cross dresser and you say No you'll get in, but if your dressing comes to light you could never tell them you were doing this before you joined or not only will you be discharged under Para 3-35 you may also find yourself prosecuted for a fraudulent enlistment. And if you enlisted or later reenlisted in a program that gave you a monetary bonus you'll be required to pay this back. An ROTC contracted cadet (which you are not) may be required to pay the cost of the college classes they'd received (I have actually seen ROTC frauds prosecuted this way). You had better stay in DEEP STEALTH if you join.
3. The repeal of Don't Ask Don't Tell does nothing for us. DADT dealt with sexual orientation, NOT gender identity or gender expression. AR 40-501 is still in effect. In fact, if you do a web search for DADT Repeal FAQ you'll find that very topic specifically addressed.
Sorry, but this is the reality as of today. Maybe it will change before too long, but don't hold your breath.