I booked going through Costco's website. I got an intermediate at Budget starting on 10/22 for $22.53 a day. Accessing Budget through Costco site automatically entered the correct code needed. Didn't pay attention to weekly rate. Also printed out a coupon for an additional $15 discount to use at the counter. I've never gone through Costco before, but assuming they may ask for your membership card at some point. I have not gone back to re-check rates in several weeks, so it could be lower. Think I will do that today.
Good luck. As we are now at less than 10 weeks away, hoping rates will start going down soon.
Mousesavers often lists discount codes for car rentals. Check the car rental sites for codes and last minute deals. National will let you piggy back various discounts.
And keep checking. Once you find something good, book it, but check again and again. I'm going in early October. I found a compact for eight days at Budget for $167 so I booked it. About a week later I found a compact for eight days at Alamo for $144, so I booked it. When I checked Alamo again a few hours later the $144 rate was gone. I'm convinced you have to be in the right place at the right time.
I've also signed up for various car rental newsletters. They'll announce special deals when they're available.