One suggestion is New Orleans at Halloween!
It's like Mardi Gras but without the drunk tourists. And it's usually not
too horribly hot.
I've got to agree that Costa Rica would also be
very sweet. It's a little tough to get to but it's safe and astonishingly
beautiful. Just as long as we don't hit it during the monsoon
season...
Maybe Iceland at the summer solstice (sunshine all
the time!).
A Burning Man style location would be super
righteous as well. The physical danger involved in the desert would mean a
lot more responsibility for the organizers but you don't have to worry much
about rain. There are plenty of really vast stretches of public land here
in the States and getting the permits for a large show is not too
expensive. You just have to guarantee clean up and port-o-potties and I'm
sure there's liability insurance.
Any other suggestions? British Columbia or
Easter Island...?