A little background on me before I start trying to give advice. I am not smart, but I am tenacious and driven. I had a very average GPA, but I have good monkey skills. My collage degree is in psychology, so don't think you need a degree in mechanical engineering to get through this. They stress that at the very beginning of API - that the course is geared towards the liberal arts type people so that everyone can understand the concepts. You just have to apply yourself and study the material. Trust me, this isn't stuff you can gaff off and think that you can slide by in. You gotta know this stuff, there is no way around it.
As far as who they are selecting right now... They need pilots. Pilots right now are classing up the very next week after they report to API. On the other hand, NFOs are having to wait anywhere between 3-5 months. (NFOs graduating OCS right now are going to class up some time after October.) I know a bit about this stuff because I worked in Student Control for 4 months before I classed up. (I'm an SNFO.)
If you have not taken your ASTB (or OAR) then I suggest getting some study material. If you do not score high enough on a certain aspect of the test, you will be disqualified to be a pilot (or an NFO depending on the section) until you can retake the test and score higher scores.
Here is a page I made to help people along with there OCS packages -
http://www.geocities.com/frogggystyle/hobbies/ocs.html
At the botton there are some helpful links. One of them will be a link to a company that sells study guide material for the ASTB/OAR. The one I bought was the Military Flight Aptitude Tests book and it really helped.
Right now they need people, so don't worry about the compeition...just worry about being physically qualified. I had the same dream you are having right now. All I ever wanted to be was in aviator. Don't wait too late or your eyesight can be a disqualifying factor (like it was for me to be a pilot). Press forward, never give up...and don't let anyone tell you no...unless they tell you three times and the last guy has more than a few bars of gold on his sleeve. hehe Eyesight is a *huge* issue. You have to have 20/40 uncorrected in each eye, less than a -1.00 diaoptic if you have an astigmatism, and not have had any vision corrective surgery (PRK, etc.) or you will automaticall be disqualified. That is for Pilot. NFO is more lenient.
Good luck!