The lobby will be the downstairs area right at the main entrance of the convention center. If you take a look at the map posted on the Cosplay Gatherings thread, BSapphire has a picture on her Photobucket that shows the exact location. And if you're still having trouble finding it, just ask any One Piece cosplayer where the gathering is. Most likely they'll know or find out with you.
Except for Zoro. You know, bad with directions.
Except for Zoro. You know, bad with directions.