HB, you can always descretely call for a cab or make round trip arrangements beforehand if the location isnt too far

If you are ready to leave, though, (for example he picked you up) the powder room is a good place for that...ask the dispatcher to have the driver call when s/he arrives...and you can always (with grace) just say, "I had a wonderful evening...thank you so much" and a nice kiss on the cheek before you depart

I have done that in the past esp when I was meeting someone for the first time at a restaurant. Took a cab there and home. It is safest to me so I can enjoy the evening, have a glass of wine with dinner or a cocktail and not worry about getting in the car or needing a ride.