Standard Camping passes are always available at the gate. I don't think they have ever sold out standard camping.
Depends on the type of camping passes you want to buy. General admission camping passes should be available on your way in
Almost, if not all, other places sell out in advance. I'd recommend keeping your eyes peeled for people who are unable to attend reselling at a discount. But to Robert's point, standard camping is pretty much always available day of...
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