kpg ~ Yes, I am almost certain you must if you you don't have any accumulated stays at Starwood hotels.
Last July prior to my stay at the Dolphin (end of August), I followed the advice on these threads. I joined spg and then applied for Amex and then called spg to request the gold status which they gave me because of the platinum Amex. I had no points and no stays at that time. I used my Amex card to pay for our rooms to gather points, etc. for a hoped for visit this summer using the points I have garnered over this past year.
mouseteacher