Are there places I can secure my expensive bike while shopping at Costco ?

You could chain a bike to one of the handicap signs or one of the trees. I don't remember seeing a bike rack.

I don't recall a bike rack, but you might call them. Honestly not sure how you'd get things home on a bike with the large sizes they sell.

Go speak with the manager on duty. Don't rely on second hand information. All locations are different.

I saw a bike rack and my daughter said they let her take her bike in once she just laid it on a flat bed cart

Yes

I never saw a bike rack.

I don't think there is bike rack at hillsboro location. There is bike rack at aloha location. I would advise to call the hillsboro location.