I flew to Kona a few days early, rented a car, and went to Volcanoes National Park. If I'd had more time to do research I would have hiked in the Waimanu valley instead, but VNP was pretty cool. I backpacked in to a pair of secluded beaches where I had small beaches and coves, with camping and snorkeling all to myself. The hiking to get to the beach was pretty underwhelming, as it was mostly lava and grass with no shade, but obviously the point was the beach, not the hiking.
After the beaches, I drove back to Kona around the island in the other direction, and it was far prettier. The rainy side of the island had huge lush gullies with steep cliffs and rivers running into the ocean. The conference itself was at a Marriott in what is likely a pretty standard resort on the leeward side. The snorkeling was pretty lame as visibility was very low, but I did see my first couple sea turtles.
Great trip. Looking forward to going back someday and checking out the windward side of one of the islands.