Well,I wouldn't advise locking to the fence. The uniformed Secret Service goons get pretty bored. I friend of mine got hassled for leaning his bike against the fence while taking pictures. Two goons,with one of them keeping his hand on his weapon. They got really ramped up when he told them about how he hadn't missed a protest in front of the White House in years. They let him go with a stern warning. Fun part is,the reason he'd been to all the protests is he's a DC cop! He worked crowd control. He only showed them his drivers license cause he was waiting for them to get stupid before he pulled out his badge.

BTW,we did play a quick game of bike polo in front of the White House once. Too open though,we kept having to chase the ball.