I suggest staying around the Polanco/Hotel Nikko area. There are some upscale bars there and the wait staff should be able to help you. As might some of the doormen. The Nikko caters to Japanese businessmen so . . .

The only time I was there on business I managed to pick up a nice local girl at a locas bar within eyesight of the Nikko. If you speak spanish and are American you'd do well there. Can't remember the name but I believe it was the a womans first name.