I prefer to do the same thing - keep the fangirling to the "appropriate" venues. And I know that I would totally either babble like an idiot, or just stand there appearing to be petrified by shyness.

Besides, I already get plenty of grief from my girlfriend for the fangirling (and the slashfics, and my crush on Patrick...) so I'm used to not being loud and obnoxious!! :)