Maalaea bay is pretty easy, if it's small craft advisories, it will usually over the top for the AI.
Outside of the bay in Maui leeward waters it's a bit harder to judge, because the area is so large and the conditions so varied. Often, we have small craft advisories on the leeward side because of large waves 10 miles on the other side of Lanai, 40 miles away. A better guide may be the beach forecast at http://oceansafety.soest.hawaii.edu/index.asp?i=maui, but be careful as it's not always kept updated especially on holiday weekends.
Another good guide, is when lots of wind surfers start heading out, it's time to come back in with the AI!
For Maui area, I've collected all the sites I use to determine when and where I sail on my weather page at: http://www.kayakingbob.com/weather
I hope to see you out on the water...