how much i need to fun in Sanya about week?

Hi, during that time, the average temperature could be about 20-22 C. It can be a nice travel season. But you may feel a little cool in the early morning and afternoon. So apart from both the short-sleeved and long-sleeved shirts, you need take along the light coat or windproof light jacket then.
As you plan to travel for nearly a week there, I suggest you find a local guide to fully view the cannot-missed attractions there.
As for the food, the abundant, pollution-free seafood resources make the seafood very special and delicious.
May you a good trip!