I want to pay a violation in person or with cash.

Whistler Parking does maintain a store-front office. 

Cash and Debit Card payments can be made at any Money Mart store in Canada. (via Telpay utility payments) 

Whistler Money Mart Branch at 4314 Main St. Map and Hours LINK

They  offer Foreign Exchange for US dollar  and other currency payments.

 Please use our internet, telephone or mail service for Credit Card Payments. LINK