I recently stayed at the Marriott Courtyard in Tukwila (Seattle suburb).
On check-in, I asked the friendly clerk about their firearms policy. She looked quizzical, and said she didn't think they had one, but would check. She went away and spoke with the manager (I assume), and came back and said, they don't have a policy. I thanked her, and didn't say anything else.
I did OC in and out once, but I don't think anybody noticed.
All odd, because I did read Marriotts have been known to not be firearm-friendly in the past, but couldn't find anything current.
If there are Marriott properties in the area you will be visiting, you might call them and see what they say.