Yes. No dought you can book your ticket by online. We did the same and visited three months before. We went from Illinois.
No you don't have to prebook, we just went early & got the sunset cruise
Got our tickets online and we were glad because it was busy.
They have a ticket window(on a boat) right next to the cruise line entry on the Riveria. You can get your tickets there. if you plan on visiting on holidays or weekends, it's advisable to book tickets in advance.
No you can buy tickets at the ticket counter. It's usually a good idea though since they do occasionally sell out.
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