Southerly winds tend to be a bit gusty, unless mixed with a bit from the East. SSE-SE can be smooth, and you won't have to worry about crashing into the pier on the south-side of the park. It's worth taking a day off work for a SSE-SE forecast!
NNE-NE winds are side/side-on wind, but tend toward gusty. During these winds, the pier could be a problem if your kite falls. Consider heading 10 minutes north to Zion under these conditions.