If you plan on using a Dragon Dance Salamence, I would go with Adamant.
Salamence is already quite fast, so after a Dragon Dance it will be very fast, which would make the Speed contribution pointless. You might as well add that 10% boost to Attack so that you can sweep successfully.
Here's a good moveset for Salamence:
Fire Blast or Roost
Item: Life Orb or Leftovers
Nature: Adamant ( Naive or Naughty, if you go with Fire Blast )
EV's: 4 HP
( Fire Blast ): 232 Atk
Hope this helps!
Ohhh, I wish I knew what you were talking about.
I'm still in the Kanto Region (pokemon Yellow :D!)