Sanya isn't as international as, say, Shanghai, but you'd not have much problems getting your "every day" stuff done there, it's still a touristic area, and I'd say English is the
#1 language used to communicate with Non-Chinese guests. (Russian being a strong second, and nearby predominately Russian-resorts it's probably the other way around)
The beaches were kept clean (public areas) to a reasonable degree, didn't bothered me. Swimming was good, but it's really hot in summer.