Got mine at check-in without asking today here at the Crystal City Marriott. But I was clearly told "it's the free breakfast
or the bonus bucks - not both". No biggie as I have a very early flight, but I didn't get the breakfast even as a Platinum.
That's OK though. When I checked in I asked if I could use a Master Card to check-in as my Visa is my checkcard which I'd prefer not to run the whole authorization through on, but that I'd switch the final bill to my Visa in the morning. They said no problem and then handed me the bonus bucks

.
Great promo though -- it's bringing me back to Marriott after about 18 mo. at Starwood & Hilton. Can't beat a $100 bonus buck on a $129 rate!