Asking for permission is definitely the best strategy. On
MyNissanLEAF.com there are plenty of discussions about the very different attitudes of different dealers, a few of which won't even allow LEAF drivers to charge (?!

). Since the Tesla is so unique (especially at a Nissan Dealer) you might find some goodwill, but, please, for the good of all EVangelists and the future of EVs, don't abuse the privilege. Definitely some Tesla time is in order, but if it were me, I would limit charging there to near- or actual emergencies. (Unless, of course, you also own a LEAF

and are on super-tight terms with that dealer's Sales and Management teams

)