Motorbikes/scooters are very dangerous - there are numerous fatal accidents every day in Phuket and I would strongly recommend renting a car if you want to get around the island.

I have been driving in Phuket for almost 3 years now and find that very defensive driving is the best approach - also don't forget that as a "farang" (foreigner) you will automatically be at fault should any accident occur, no matter how minor.