R.J.
We got ours from a breeder (sticker shock!)... So I can't help you there... But the off leash parks (Magnusson... Don't follow the signs -typical Seattle signs don't send you the right way, we had our dog off leash in the wrong part of Magnusson for months, blithely unaware along with a dozen others-, Go through the main enterance on Sand Point Way, go straight until it deadends at the dog park just past the playground. Actually, we do both. Dog park then people park!) Or.. Edmonds & Marymoore also have OLDPs.
Magnusson & Marymoore both have message boards, all have LOTS of dogs and people out and about. Rare for Seattle, dog people all talk to each other / strangers.
You won't see a lot of puppies ever, most vets rec no parks until 6mo old, and it MAY be a park rule... But lots of dog people!