Most of the Hawaiian cruises out of San Diego visit Kona on the Big Island of Hawaii. The Kona Coast is the sunny, dry west coast of the island. That makes it ideal for vacation fun.
Kailua Village (also known as Kailua-Kona) is the town at the center of the area. It has the restaurants, shops and nightlife.
There are numerous historic sites around Kona. These include Hulihee Palace (a summer home for Hawaiian royalty), Kealakekua Bay (where Captain Cook first set foot on the island and where he was killed), and Puuhonua o Honaunau National Historical Park.
Sip famous Kona coffee and see the coffee plants. Go snorkeling. See dolphins and sea turtles.
The video below is about a cruise ship's stop at Kona. I think you'll find it informative.