Don't bother with your congressman.

When I was a visa officer in New York, letters from members of Congress or Senators did nothing but move a file to the bottom of the pile. Phone calls moved the file back to the shelf.

A few other tips:

1) Get the visa before you go. There is nothing like an ugly delay halfway through your trip to ruin your plans.

2) Rather than Fedex, prepay a UPS waybill. A lot of visa offices will no longer accept or use Fedex, because if the account on the waybill is a dud, then the charges get applied to the sender. Better still, prepay ExpressMail. No arguments there.