Smathers is pretty much it for Key West unless you are highly motivated and willing to take on some extra, perhaps a lot of risk. Key West has only one designated launch, that is at the extreme west end of Smathers Beach. Perhaps Greg has something to offer on this. See what the Florida KB Guide has to say about rideable wind directions at:
http://fksa.org/showthread.php?t=2278
The Kitehouse runs regular sea taxi out to the Key Flats rideable in winds from all directions. This has been highlighted in articles for some years now. Pretty interesting write ups too, surprised you never saw them before. If you're going to drive all the way to KW, best to plan on time out in the Flats in all that butter, shallow warm water, no powerlines, smelly beach bottom, etc..
More at:
http://fksa.org/showthread.php?t=427
http://fksa.org/showthread.php?t=5358
http://fksa.org/showthread.php?t=4846
