Oakland Nature Friends club is an amazing German hiking club located in the Oakland hills. They are open to the public for their annual Oktoberfest celebration. The festival will feature polka band, traditional group dances in traditional dress, a menu of traditional foods and, of course, excellent beers complete a fun-filled day for all ages. Tickets to the event are $10 and can be purchased at the club on the day of the event.
I will be hiking to the club with my hiking group (http://www.meetup.com/Golden-Gate-Hikers/events/130848022/), but if you would rather just join for the beer-drinking and polka I am also hosting that for BABS.
There is some parking at the club but it is limited (and DO NOT drive if you plan on drinking). There is also a bus service from Fruitvale BART to some of the nearby streets (though many of the AC Transit buses do not run at weekends, so be sure to check the schedule).
To find the group, look for name tags or a meetup sign.