If you are looking for flat water the most popular spot is Osbourne Park off Peel St, Good in NW and NE. Best sailed with delta style weed fins
I go up to Halekulani at the sailing club. heaps of kite surfers get up there. i know some of them well. good to race around with. Went to north entrance the other day with lisa and lance. was around 15-25knots at most and had a blast.