The Kauai forum is pretty quiet on this subject - I haven't seen a new post in a while. So I thought I'd share some of the information I've found so far.
Kauai is known as the "Garden Isle," the oldest and northernmost of all the Hawaiian islands. It's the least commercially developed, thus preserving a lot of its national landscape. The island seems to be broken down into five parts as seen in this map:
- North Shore (Anini Beach, Haena, Hanalei, Kalihiwai, Kilauea, Moloaa Bay, Princeville, Wainiha)
- Coconut Coast (Aliomanu Bay, Anahola, Kapaa, Kapahi, Kealia, Wailua, Waipouli)
- Lihue / Kalapaki (Lihue, Nawiliwili)
- South Shore (Kalaheo, Koloa, Lawai, Omao, Poipu)
- West Side (Eleele, Hanapepe, Kekaha, Makaweli, Waimea)
Princeville contains the more upscale resorts (e.g. St. Regis Princeville). Princeville and Hanalei seem to be the more popular sites for wedding ceremonies as they have the best views of Makana Mountain, made famous as Bali Hai mountain from the film South Pacific. I've seen pictures and advertisements for weddings at Hanalei Colony Resort, Hanalei Bay Resort, St. Regis Princeville, and Na' aina Kai Botanical Garden. Be warned: this area is likely the most expensive. The North Shore has quite possibly the best views on the island - perpetual rainbows, breathtaking sunsets, and romantic mountain views. However, it rains nearly everyday - more often mists and droplets, with occasional downpours. So keep this in mind when planning your ceremony.
Kauai's East Side is called the "Coconut Coast" because of the coconut palms that grow in its resort areas. This area is the most populated on the island - so it's likely your vendor is based out of this area. Most residents live in the Wailua / Kapaa area. Should you decide to have your wedding in the area, your guests will have plenty to do: shopping in Kapaa Town, kayaking in the Wailua River, boat ride to the Fern Grotto, and hiking up Nounou Mountains. It's generally recommended that you rent a car if you want to explore the island, but if you were counting on public transit, the Wailua / Kapaa area may be your best bet since most residents live there.
Some popular wedding sites: Kauai Coast Resort at the Beachboy (right next door to the property is Hukilau Lanai, revered as one of the best restaurants on the island. There seems to be a partnership between the two establishments for weddings), Smith's Kauai (Fern Grotto is located within this establishment. Smith's is famous for their luaus).
Lihue is the first place you'll see in Kauai: it's where the airport is located The only wedding site I've seen in this area thus far is the Kauai Marriott Resort.
Famous for Poipu Beach (at one point named one of the best beaches in the United States), the South Shore is packed with places to have your wedding at and serves as a great home base for folks who want to explore Kauai's West Side. You'll have plenty of venues to choose from: The Beach House Restaurant (gorgeous views and consistently rated as having excellent cuisine. However, some have complained that the service is snooty, with the servers less than gracious - this info is from yelp, Tripadvisor, and this bride), Plantation Gardens Restaurant (they are located in the Outrigger Kiahuna Plantation. You have the option of using a grassy knoll overlooking the ocean if you stay at the Outrigger Kiahuna Plantation for $100 - there are limitations on wedding arches: you can't put stakes into their lawn), Grand Hyatt Kauai, Sheraton Kauai Resort (they are currently undergoing revitalization from January - Summer 2011), Marriott's Waiohai Beach Club, Southshore Visitors Center Garden and McBryde Garden (National Tropical Botanical Garden).
The West Side is home to the stunning Waimea Canyon, dubbed by Mark Twain as "the Grand Canyon of the Pacific". There are two main towns here: Waimea and Hanapepe. I've only found one place so far to have your wedding at: Waimea Plantation Cottages.
I recently received recent (March, 2011) pricing information from the Plantation Gardens, and am waiting for Hukilau Lanai's quote. If anyone's interested, PM me. Stay tuned! I'm compiling information about beaches and private estates, as well as photography, hair/makeup/nails and florists.