To get to Prospect Park, you may be able to scrounge a ride with one of the crew, if there's room that is. Otherwise, a cab should cost around $15. Taking the subway is a good option, with Prospect Park being served by the F (at the 15th St, Prospect Park stop), the 3 and the 4 line to Grand Army Plaza. We always gather near the Picnic House (see red circle on map).