Another warning (might as well get it out of the way off the bat so you don't waste your time if it's not something you want to do:
PHAP isn't for everyone. It's hard, you'll be uprooting yourself away from your support systems, and the transition is very difficult for some people, and you may end up in some godforsaken place you hate for 2 years. Public health is a small world, but it's also a world with a ton of turnover. People are people wherever they are, and you will be under some fantastic people and some people that will make you go to bed at night in tears.
For some of you this will be your first job out of your bachelor's degree, and though you will be extremely prepared and competent - they don't let you in if you aren't - you will get to your host site and they will look at you as either the savior they've been hoping for, or the intern. Don't let them see you as the intern. And DON'T let them call you an intern, either.
Some others will be coming out of their MPH or MS or MA or (I kid you not) PhD or MD or DO. This program can be extremely beneficial if, like me, you have the degree but not the experience in the field. Fair warning, though, if you are (also like me) someone with lots of professional experience in general or are older, there are going to be times where you are pulling your hair out because you're watching another required webinar telling you don't wear sweatpants to the office and take a shower at least a few times a week and make sure you don't chew bubble gum in meetings or use comic sans font on your letterhead and be sure to return your emails. The program will have a lot more people with BA/BS than with graduate degrees, so a lot of the training may not seem relevant. Number 2 rule, though: Shut up and color. That's not meant to be insulting. That's something that my dad used to tell me, and some in the military may say when you think you're better than the task at hand and you shouldn't have to do it. Sometimes, you just have to shut up and color.
The number 3 rule (after rule #1, which was chin up, head up, and roll with it, and rule 2 above) is: THIS PROGRAM IS WHAT YOU MAKE OF IT. Go into this with a goal. The program, when I went through it, was 200 people, and it was ungainly. Even at 120-140, it's big, and they try hard to be what I call "omniplastic" - trying to be all things to all people at all times, but the problem with that is is that they make generalists. If you do not have a plan for what you are trying to get out of it when you start, you will (surprise!) get nothing out of it. Find things to learn, get experience and certifications and take classes and expand what you want to learn/what you know and volunteer for everything.
Federal resumes are different than regular resumes (not this time, though, I think they may be limiting you to 2 pages, but check the application to be sure) but I will use it as an illustration: when I got to PHAP, I was 33. I graduated in 2007 with a BA and had a few jobs, then went to grad school to get an MPH. My resume was 2 pages, and I left off some stuff, but it was a normal resume.
When I finished PHAP, my resume was 12 pages long. Sure, I figured out how to write my previous experiences in such a way to get credit, but my PHAP resume alone was 8 pages. Of single space, .5 margins.
Say. yes. to. everything.
Even if it doesn't get you to CDC, it WILL get you a job. And what's more, you will be light years ahead of people who didn't take advantage of the experience you're about to get.