Thermal comfort is somewhat idiosyncratic.
To put it in perspective, below is a piece, in part, from my June '00 "Ask RSD" column in "Rodale's Scuba Diving":
"Have you ever been out on the street in the spring or fall and noticed people wearing everything from shorts & T-shirts to full coats with hats & scarves, all apparently in comfort? Well, things are no different underwater. This comfort is highly variable among individuals depending on such factors as percentage of body fat, age & tolerance to thermal discomfort. Other determinants, like how many dives a day over how many days you are planning, are also important. When you ask 'What wetsuit should I wear?,' you'll get answers ranging all the way from 'just a bathing suit' through '5 mm full.'
The question is better asked: 'What water temps can I anticipate at my destination?' You'll receive a pretty accurate answer to this, and then can decide what's best for you based on your personal thermal comfort needs.
It's always a good idea to come thermally prepared, just in case."
That having been said, next month look for Coz water temps of ~82 degrees. Personally, if was doing multiple dives over multiple days at that temp, I'd take a 3mm full & beanie, although you being a PNW diver might find that excessive.
Whatever you decide, just a bathing suit is an unwise idea. Because Coz is drift diving in currents that sometimes can be powerful & changing, it's smart to wear a full body covering of some sort, even if it's just a skin.
Best regards.
DocVikingo