I have only seen one property list clearly at the front desk the hold amounts placed on cards. The Fairfax Marriott at Fair Oaks has a placard with the amounts they place on hold for credit and debit cards. From my memory, it was somewhere around $50/night for credit cards and $100/night for debit cards. The debit cards had a higher amount, and the placard also listed how long it would take for the holds to come off the cards (somewhere between 3-5 business days).