Don't let the water temp worry you. I dive a 7mm semi-dry year round in the Sound. A semi-dry is just a wetsuit with wrist and ankle seals to reduce flushing. Cold surface interval gets me more than water temp. October is a great time to dive in the sound as wetb4igetinthewater said. I would be happy to dive with you, but I might be out due to shoulder surgery depending on your arrival date. I also suggest Redondo beach in Des Moines, Sund Rock, Edmonds UW Park. I would also throw in Mukilteo T-dock as good all-around dive sites for new divers. Muk can be current sensitive but easy to manage. Look at PlanYourDive.com, a local website that gives dive site descriptions, viz reports, and local tide/current information. Shoot me a DM when you determine your arrival date. Where are you planning to stay while in town? This will help us recommend dive sites close to where you are staying.