No, you don't run a PFT right away. You run an IST, which you should run several times before you even go to boot. At the rifle range (about half way through training) you run the initial PFT. then before you head out to the Crucible you will run your final PFT. This is the one that counts, so go all out on it. Btw, its the Marines... you get trained for everything you do. Whether its formal or informal lol. Hell, they even 'train' you on how to eat properly while you're at basic.