Yes, once you are in the gates (they have to let you in with your reservation so you can check in!), you just park anywhere. They don't check the parking passes. Also, you can still get your parking pass even if you don't get your room (that's what we did). So after we came back from shopping (before we got our room) we just showed the parking pass to the gate attendant and he opened the gate.
There are two gates - one that has an attendant and one that only takes the room key. So just make sure you go to the manned attendant gate when you first come in - they will ask to see your reservation, and then if you leave, make sure you get your parking pass first, and then go back through the manned gate to get back in with the parking pass.
Once you have your room, you can bypass the manned gate and just go through the gate that uses the room keys.