If you're in one of Europe's major cities on a comfortable budget, you can charge, normally, about what you can at home. Use your cards as much as possible and take advantage of the better exchange rate. Carry enough cash and travelers' checks for the balance, plus a reserve fund. Don't count on the availability of ATMS which both accept your cards and work. Ponder the question, but don't voice it.
Legal currency is real money, whether marks, francs, pounds, euros or dollars.
Most establishments now post prices in both euros and local currency. With the euro worth close to a dollar, the euro price comes pretty close to the dollar cost. Julie carries a circular sliderule preset with the exchange rate. Others carry calculators. You can bypass making up your own conversion chart by going to our Cheat Sheet for Travelers .