I was in Palau July last year. Weather was not great. I'm going back in January. Doing Palua, Yap, Chuuk, Kosrae, and Pohnpei.
Can't beat the Palua Pacific Resort and Sams Tours in Palua.
I would go Dec-March. Be sure to visit the story board bar, Kramers Cafe, the bar on the NECCO marine...