Do not assume you can find a cab at 19:30. Even if it's Wednesday, the weather is lovely and you're in the middle of the city. Being dressed to the nines for an evening at Pre Catalan will not help. The Parisian taxi driver won't be impressed by your cufflinks. He already has a fare.
What should have been a pleasant cab ride through the Bois de Boulogne towards one of the best restaurants in Paris ended up in a hellishly stressful hour plus search for a cab. We finally gave up and took the metro to Porte Maillot, nearer the restaurant and with a cab stand. Even there we waited 10 minutes.
Time to learn how to reserve a taxi by the phone.