In May, we plan to wear shorts, t-shirts/tanks, and comfy shoes (crocs, tennis shoes and some water sandals/tennis shoes). Pretty much most of our clothing will be of the 'dry quickly' variety -- so water shorts (basically quick dry hiking shorts) for the DH and light-weight shorts/capris for me.
The quick dry goal is what we aim for, too. We are going in June and will either be rained on or get wet on rides. I hardly ever wear cotton because of this. We tend to wear a lot of polyester or nylon microfiber and rayon. It also looks nicer if you happen to be going somewhere a little upscale to eat.
A lot depends on when you go. In the hot and humid months shorts and strappys. When we were there in December it was jeans and t-shirts with cardigans for me as it got quite cool at night.