Buying tickets online for me and guest. Do they check Washington ID for local discount for both parties? Guest lives in Washington but hasn't received local ID yet.

They may or may not check ID's. Have something that shows proof your guest live in WA. Call customer service and talk to them directly.

Residents of Washington state are given discount on tickets. You need to show some id. In my group , my friend worked at Microsoft and was a local so he showed his office pass.

No IDs were checked. We went straight in. 2 guest were from California

Does your guest have anything with the Washington address? Yes, ID's were checked when I was there