If you can afford to pay the deposit now (or soon), then go ahead and book an on-site room. You can always rebook if the rates drop, or you can always cancel the reservation if you decide to stay at another location. My personal opinion is to stay on-site and enjoy the bliss of express pass. Busy days, it saves a lot of time, and on slow days, it allows you to easily ride your favorites over and over (and over and over) again. Seriously, as pcstang said, you will get spoiled by express.