The best way for you to get a firm answer to this question is by continuing to contact pretrial services or supervised release until you are provided with a definitive answer. Many jurisdictions in Washington State prohibit the possession and/or use of Marijuana on supervised release even if the individual being supervised has a medicinal marijuana card. This is due to the fact that possession and consumption of Marijuana is still federally prohibited, regardless of what the State of Washington has chosen to do. As such, my guess is that you would still be prohibited from smoking marijuana while out on release as marijuana will still be considered a "controlled substance" under federal law after December 6th. As I mentioned earlier, however, the only way to be certain is to get a definitive final answer from pretrial services either by contacting them yourself, or having your attorney do so. The last thing you want to do is get a violation and end up getting held in custody during pretrial proceedings due to any misunderstanding.
Disclaimer: This answer does not constitute legal advice. I am admitted to practice law in the State of Washington only and cannot practice law in any state outside of Washington. This information is based on general principles of law, as well as my general experience that may or may not relate to your specific situation. This information is not meant to take the place of actually consulting an Attorney in your jurisdiction. If you would like legal advice, I would recommend consulting an attorney in your locale.