I used to work outdoor vending at Disneyland. The thing about the caramel corn is while there is a standard "recipe" most don't know how to make it and just wing it. I know I did back in the day. It rarely tastes the same between trips or carts. Hit or miss.
It takes FOREVER to make so be sure to ask the vendor if they are making any and then camp out. You can only get a few servings out of a batch and it sells out quick.
Unfortunately other than the one in DCA which has been posted I am not sure which ones are still open.