We're going to Maui end of June and I have been looking for the past few weeks. General statistics say that this is pretty early and a lot of discounts come out 2-3 months prior to your dates (this is our 3rd trip, and this does seem to ring true).
With that in mind, I did just book a convertible through
Alamo for 10 days at a cost of $574. That's high in my opinion, but I've been seeing them in the $700 range. I do believe it will go down below $500, so I will just keep looking and cancel when I get it cheaper, but for now, there is peace of mind that at least I have the car I want for a somewhat reasonable price.
I used the visa code AD7394SDJ, and signed up for their insiders program which gives an additional 10% and allows a second driver for free. I found this to be cheaper than costco, discounthawaiicarrental, and any other site I've checked recently.
If you haven't found tripadvisor dot com yet, that is an invaluable site for planning my hawaii trips, lots of great advice on there