If I come up on PCS orders can I still use my Reenlistment window to choose a new station of duty?

You'll definitely be on assignment by then, and once you're on assignment you can't reenlist for anything but the assignment. If you're OCONUS you should contact your branch manager no later than 7 months from DEROS to work your next assignment.

SPC, when I Korea I was trying to reenlist to continue my overseas tour; however, I came up on orders to PCS to Forth Hood and my retention NCO told me I could only reenlist for needs of the Army or sign a Declination statement and get out. I had no option but to reenlist for Fort Hood. I still tried to stay in Korea by submitting an IPCOT which went all the way to HRC but my request got denied. I will still encourage you to do what you can if you really like your unit, I know of people who had orders and managed to stay. Depending on where you are you can do IPCOT, COT, FSTE, AIP, or simply request a cancellation of orders if you have a legitimate reason for it.
I will say thought, I'm happy my IPCOT got denied because I'm currently in the best unit I have ever been.

If you've never relisted before, you can wait until you get to your new duty station to reenlist for a different one as long as you are not fenced in. The army only requires you to do 12 months at a duty station before a pcs, all other timelines are policies (36/48 TOS erc.) But can be waived especially for a first term soldier reenlisting. I would wait until your next post and then reenlist for what you want and pcs after a short time there rather than doing it now and being stuck for 36 -48 months at fort wherever.