Kingneptune, wrong attitude my friend. I completely agree with you that flight training is expensive. But there are ways to get around that. I started hanging out at airports when I was 15, and you wouldn't believe some of the flying opportunities I have had by just talking to the pilots there. When you see a guy pulling his plane out of the hangar, offer to help him out. Hang out in the restaraunt and ask questions to the pilots that come walking in. "Excuse me sir, but I saw you taxi up in that cool plane out there. How fast does it go?" Just ask a question or two, and more than likely he will go on and on talking about how great his plane is and how awesome he is at flying it. Sit there and look interested in everything he says and be proactive in the conversation. You want to take note of things like whether he or his buddy is a CFI, and owns there own airplane.
Next thing you know he might say something like, "I'm going to be flying it this Saturday to test my new altimeter/transponder/VSI etc., wanna come along?" After the flight, tell him that you are very appreciative of him taking you flying and that you would like to express your gratitude by washing his plane, sweeping out his hangar space, etc. Things like this speak volumes about your character and love of aviation. If you stick with it, you can eventually get a PPL for cheap. You will also probably meet AF pilots who, if you play your cards right, you can get an LOR from them later on.
Now, why did I mention all of that? Because you will be competing for AF pilot slots with guys who busted their butts to pursue the aforementioned route with success. You mention about going ROTC. That's fine. Back in my ROTC days, our Det. Commander told us something to the effect of, "If you guys want to get a pilot slot, I had better see some serious attempts by you to get your butt off of the ground." Sure, there were guys in my detachment who didn't have a PPL that got slots. However, EVERYONE who had their PPL got pilot slots (as long as their other scores measured up ofcourse.) Coincidence? Maybe, but I personally don't think so. Getting a PPL says a lot about a person. Besides, there are several on this forum, myself included, where ROTC didn't work out.
If you're worried that spending all of that money for a PPL would be wasted if you get Med DQ'd from AF pilot training later on, then you had better do some serious soul searching and ask yourself if flying is really what you want to do. I have yet to meet an AF pilot who didn't have a strong passion for flying in general. Another common characteristic is the fact that they would do whatever it takes, for as long as it takes, for the opportunity to fly. That attitude is a strong contributing factor for success at UPT. It seems to me that you are more focused on having those shiny wings on your chest, as you face the sky with a silk scarf fluttering in the breeze. If you should get Med DQ'd for something that can't be waived, wouldn't you feel better going through life knowing that you gave it everything you had? I suggest doing some research and asking questions about what AF pilot life is really like as well as what it takes to get to that point.