Yes, you can.
During show days. You can
I believe you can do that & will call. I have ordered them online & picked them up at the box office before but most times they are mailed directly to my home. The advantage of ordering online is getting the best available seats at that moment. Going to the box office would be the same but unless you live extremely close to the playhouse then you may not get the seats you wanted when you saw them online. Online purchasing is always going to give you the best seating options available at that time.
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