I always like to go out for dinner on a first date.  Not only is it a safe environment, but you can also see her eating habits first hand.

Did she order a steak?  That is good.  Did she order the fish?  Well, OK.  Did she order the Tofu and Eggplant stir fry?  Maybe you need to talk.

And while diet is not a show stopper, it might create complications.