When we were there in June and July, the GCH entrance could be used by any DLR hotel guests and you had to show the room key. They were strictly enforcing the policy and I saw many people turned away that were not DLR hotel guests. This has also been a published perk for DLR guests only but was never enforced. They started to enforce it once WoC debuted. I have been told that if you buy something at the hotel, like at Whitewater Snacks (can be small) and show your receipt, that they will allow you in.
Check with PPH when you arrive to confirm, but they have been letting DLR hotel guests into DCA one hour prior to opening to get Fastpasses for WoC. And yes, Soarin' does open 30 minutes prior to the rest of the park.
Have a great time!