Yes. I was able to make one last year simply as an onsite hotel guest. You may also be able to get in just by walking up--this has worked for other posters here.
I don't quite recall the limitations. I think maybe I could only do it a few days before--or I might be imagining that. I also don't remember if I had to prove I was a guest of the resort by showing my room key. It's one of those things they do but don't really spell out anywhere how it works.
Stay tuned to this thread and maybe someone else can answer. Or, perhaps you could call HRH and ask for the Attractions Tickets desk--it was called something like that. Good luck!