Hi everyone, we are planning a trip to Universal over Thanksgiving and staying off-site. We want to purchase Express Passes for the three days we are there, but I'm hesitant to buy them in advance because you have to specify the dates. What if you have to cancel - you're just out the money, right? If this is the case, maybe it's better to purchase them when you arrive, but do they ever sell out of them? I mean, will it be a sure thing that they will be available if I buy them when I arrive?