We live fairly close to there, it's a nice park, right on Lake Washington, and if there's nobody around, your Yorkie can get a taste of sand and the beach (though the water is a bit dirty around now)!
Yoda had fun tonight when we went, met a little Zorro (black and white, no clue what breed), and Zorro was a bit tinier than Yoda! We usually let him off leash, it's generally not too a crowded place. Yoda just loves free open areas for which to roam, and trees for which to mark!
Matthews Beach Park
9300 51st Ave NE
http://www.cityofseattle.net/parks/p...s/matthews.htm