Pretty pricey for taxi from Patong to Ao Nang. Last time I checked it was about 3,500 baht. Problem with bus it that you catch from Phuket Town (not Patong) and it takes you to Krabi Town. I've heard that there might be a minibus service from Patong to Ao Nang once per day. You would need to check with any tour desk once you get here. A self drive hire car might be a good option, but you need IDL (International Driving Licence) and agreement to take hire car off Phuket Island.
Edit just checked the price at
http://www.phuketshuttle.com/ quote 2,500 baht Patong to Ao Nang.