Generally a good idea to pick some starting point that is easily identified, has lots of space, doesn't object to a gathering of car nuts who want to look at each other's cars. Then a drive through interesting scenery and twisty roads to an interesting destination. One where food and beverages and a sit down discussion on one of our favorite subjects can occur. Then a split off depending on where people are headed back to.
So you be the organizer ....
Post here and on
www.ppbb.com and see who you get. Maybe the first time there will be a few but if you chat up what a good time you had on those same forums, the next time the group grows. Suggest not limiting it to Boxsters as any P-car or other interesting car will make the discussions more fun.
I'm doubtful as I'm moving in the next 2.5 months. But maybe .....