The easiest place will be via Hong Kong via Dragonair [KA]. Dragonair flies to both Haikou & Sanya.
Other places include Macau (Air Macau), Kuala Lumpur (Hainan Airlines) and Singapore (Tiger Airways, which is a budget airline, and China Southern Airlines).
The flights from Singapore fly into Haikou.
From China, the nearest cities will be Shenzhen and Guangzhou.
Most public buses in Hainan is RMB1/person, but there are also several buses need RMB2 or RMB3, or even RMB5. Such as NO.40/NO.37/NO.39... in Haikou, tourist buses in Sanya, RMB5/person from Yalong Bay to Tian Ya Hai Jiao. It charges as the journey.
There is public shuttle buses on the first floor of Haikou Meilan Airport. RMB25/person, destination is Haikou Civil Aviation Hotel, which is located in Haixiu Road, Haikou downtown. It takes about 30minutes. If you want to take the bus to the airport, also please buy tickets and wait at Haikou Civil Aviation Hotel, there is a bus every hour, such as: 9:30, 10:30, 11:30...it must be departure at **:30 o' clock.
Bty, no matter you are passengers or not, you can take this bus. Just need to pay RMB25/person.
Even the guidebooks get this wrong (Roughguide and Lonely Planet). To catch the long-distance bus from Haikou to Sanya, you have to go to the Eastern Long Distance Bus terminal. Ticket costs 79RMB for first class Express - which means air-conned and a bottle of water. Tickets should be available on arrival . On buying the ticket, go to the boarding gate and look out for the arrival of the bus. Each gate has an electronic call screen though the conductors usually prefer to yell out (in Mandarin) for the passengers so just ask if you are not sure, less in case you miss your bus!
The cheapeast to get into Sanya town from Dadonghai is via Public Bus (which is green in colour). The most travelled route is from Dadonghai to the Long Distance Bus Station. The entire journey only costs 1RMB. Not more; not less.
There is a bus connecting the 2 ends of Sanya from Tianya Haijiao Park all the way to Yalong Bay with Dadonghai beach smack right in the middle. The entire journey takes slightly over an hour and cost 10RMB. Best way to see the coastline of Sanya, especially the stretch from Dadonghai to Tianya Haijiao Park (5RMB). Extremely scenic! Also the cheapest way to get to this 2 popular destinations, no matter what other folks say. There are bus-stops and this special bus is the only double-decker bus in service. The lower floors are air-conned; the upper floor al fresco.
There is an Airport Shuttle from Haikou Meilan Airport into the city. Should cost you around 25RMB. This is the cheaper ride compared to haggling with the taxi-drivers to drive prices down to about 50RMB. The shuttle bus will drop folks off at specific stops but the best bet is to go straight to the terminal and then grab a taxi for 10RMB for any travel within the city limit.