Yep, but if you preordered online and paid full price you cannot switch to the upgrade program.
I chatted with Apple and I was told that even if you did put a reservation through the iPhone upgrade Program, you can still buy it outright and not have to use the iPhone upgrade Program. Which I may very well pay it outright instead. What the reservation system does is it just reserves the phone for you and you can come pick it up, you don't "have" to use the iPhone upgrade program.