Unfortunately, you’ll have to shop around to see who has the cheaper price. Alamo insiders get a 5% discount on their reservations. You can sign up for free. Costco Travel may have a cheaper price, but you won’t know if they do until you put in your dates. I wouldn’t recommend paying upfront for the rental, but you do need to reserve it. Aulani Alamo often doesn’t have any availability for walk ups. If you find that Costco has a cheaper price, you can cancel your original reservation. That’s what I did my last trip. I first booked direct with Alamo. I never prepay for my reservation in case I change my mind. Once I saw that I could get a cheaper rate with Costco, I booked the cheap rate with them and cancelled my other reservation. Make sure you bring your confirmation with the price on it when you pick up the car. The rate Alamo said I would pay was slightly higher than what Costco quoted. Since I had the confirmation paperwork Alamo gave me that price. The agent said the difference had to do with how they figure the taxes.