MERICANS SHOULD AVOID TRAVELING ALONE, PARTICULARLY VIA MASS TRANSIT AND AT NIGHT. 2. VISA/PASSPORT - A. U.S. CITIZENS MUST HAVE A VALID PASSPORT. B. U.S. CITIZENS DO REQUIRE A VISA AND IT MUST BE OBTAINED PRIOR TO ARRIVAL. C. DUE TO A NEW REGULATION, THE CREW WILL ALSO HAVE TO HAVE A LETTER OF INVITATION BEFORE THEY CAN OBTAI