July 4 I would buy advance tickets.
Also, ask what how long the wait can be. The time I went I had to wait 2 hours before I come place the order. Once you order the service is fast.
You can just show up but in my experience, the hours online are inaccurate. I went on a Thursday and they weren't open until late afternoon. I suggest calling a day in advance to clarify the time they open.
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