So far I haven't needed to bring my 2018 Zero (or my 2014 Zero S, for that matter) to my dealer, other than for motor "commissioning" at 600 miles. And frankly, I am not at all sure that the "commissioning" actually did anything noticeable. Firmware updates work just fine via an internet download directly to the bike's computer by way of a cell phone Blue Tooth connection. Still, if I was in Hawaii, I would contact Zero and see what they have to say about dealing with any service or warranty issues at your location.
I wouldn't worry too much about the problems that you read here. Like all product forums, all you read about are the occasional major problem. You never hear about all of the people who are happy with their Zeros. What you really want to know is what is the percentage of people who have problems that they can't resolve themselves, compared with Zero customers who have no problems at all. Unfortunately, your guess is as good as mine. Likely only Zero knows the answer to that and they aren't telling - just like every other vehicle manufacturer.