I am staying off property next week but was hopeful to pop in and have a spa treatment at Saratoga Springs. If you aren't a Disney guest, are you unable to use the spa or get the DVC discount?
You should be able to make a spa reservation, and show your DVC Member card for any available discount. The spa are is not operated by Disney, they are an outside contractor.
I have the new Perks pages and it says specifically to bring your member Id and your Key to the World card to recieve the discount. BUT when I used the Spa at Saratoga Springs, I paid cash, booked the members spa special over the phone and they did not ask for either.. Go figure. I just want you to be prepared. I'd try it myself.