I doubt a PPL will make a difference in getting to UPT. My experience is old (20 years) but I was never asked the question until I showed up. I went through the Flight Screening Program in Hondo Texas. Everyone went through the same program regardless of experience. Several with a private dropped out others were eliminated. If I remember correctly they either could not or would not adapt to the way the Air Force wanted them to fly. Generally that is to fly in a strict procedural way not just a safe way. By the way lots more without any civil time did not make it through either because they could not solo in the prescribed number of sorties. When you get there you have to make it within the syallabus as opposed to before your money runs out. Best of luck!