I think the Radegast Beiergarten in Williamsburg (http://nymag.com/listings/bar/radegast-hall/) would be a great place to meet (long tables, beer steins, sausages) and it's very accessible for people of all boroughs (first stop in Brooklyn on the L-Bedford Ave). It tends to get crowded on Weekend nights but should be comfortable on a Sunday evening.

Full Disclosure: I live in Williamsburg. That said, I'm more than open to any other location in Manhattan or Brooklyn.