Richard is correct in that the 3-6 month wait is specifically before you can be considered medically qualified. However, there's a nice little question on the initial application asking specifically if you have had anything along the lines of PRK, so talk with your recruiter, and equally important, your processor before counting on getting the app in before those 3 months. I didn't submit any MEDDOCS regarding the surgery until I went to MEPS, but I also noted on my application that my surgery was done 6 months before I submitted the package for PROREC.
But if you're trying to figure out when to get the surgery, the application timing will figure itself out (generally, "as soon as possible"). Yes, get it done ASAP. Take the recovery time to do things like study for and take the ASTB. If you find a particularly !@$#-hot surgeon, they'll be booked a month or two out at least. I had to wait 4 weeks for an initial consult. Start finding doctors and making phone calls as soon as you possibly can.