+1 on you have to at least try poi... they have huge taro fields just outside of Princeville-Hanalei.
Still think Hanalei is the best if you want to just kick back on the beach, there are some resturants/bars/shops right there in the Hanalei village.
IMHO best fish can be had at small local fish markets.
Beach at Hanalei (my brother and family):
