Yes you can use it even without a membership Or Even you can ask for a tryout with a free pass for one time !
Anyone can use a Costco giftcard at any Costco even if you do not have a membership.you can look it up on Google it clearly states anyone with a giftcard can make a purchase at Costco anywhere in the US and Puerto Rico.
You can go in with someone who is a member
No, members only. However, you may be able to make a purchase on costco.com.
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