Can we use cash at the Costco gas station? And will they accept Visa debit cards?

Only visa, any visa card. No cash at all.

No cash. Maybe a cash card

I believe you can use a Costco Cash Card to purchase gas from Costco and you don't need to be a member. You just need a member to buy the Costco Cash Card which is basically a gift card for Costco

Its only with the card and u need a membership