The easy answer is that NO there is never a bad time to go to Desire...lol.
Ultimately, it comes down to weather. I'm not sure what October is like but I'm sure there are places that will give seasonal averages. We tend to like spring...April/May. Hot, but not too hot (weather wise!!)...with a nice breeze off the ocean. As you get into summer it definitely gets very very hot from what we've heard. Reports from late fall, winter seem to be that the pool and such get too cold to enjoy.
In terms of "non takeovers" our first trip there were no takeovers, so a mix of nudists, swingers, voyeurs, exhibitionists, etc. We went with a takeover last year and had a blast. Again, it depends on what you are looking for in your trip.
As for a good time...hmmmm...I guess I'd have to say when Swingercast is there