Americans are saying "OK!" to European vacations this year. Thanks to a falling euro, savvy travelers can go abroad at bargain prices, a welcome cost "u-turn." Mathew, New Yorker: "That might change things but in the past like last summer I went there, it was very expensive!" Travel agent Yannis Moati is pushing his clients to make the most of current exchange rates.  His New York office introduced an "Anti-Recession" tour: Vacationers can traipse through Venice, Florence, and Rome for a week, at 1160 per person.