I always use the Roissy bus option to Opera. 8.50 euros each way. They take credit cards on the bus. Departures are about every 15 minutes. As fast or faster than a taxi. Short walk to PH Vendome. Just get good walking directions first or you can get lost easily. When you get out of the bus, the Opera House is across the street on your left. You head out keeping the Opera House on your left. You cross the first street at a light and then you are on Rue Scribe. You walk by the IC LeGrand on your left, Old England on your left, and Hotel Scribe on your right. Cross the next street and you are on Rue Daunou, and will pass on your right the monstrosity that is the American Dream. If you take the next right, you will arrive at the back entrance of PH Vendome on the left in about a block or so. If you take the second right, you will be on Rue de la Paix and the front entrance to PH Vendome will be on your right in about a block or so. Bon chance!