Well those who worship Eilistraee are only really concentrated (in any numbers) at the Promenade (under Waterdeep) and around Cormanthor. So it's unlikely any non-drow would have come across an actual worshipper.
It's possible that the Dylan may have heard something of the Goddess, but I think it'd take quite a high check to be able to recognize her holy symbol.
Of course this kind of stuff is really up to Kaelyn.
Feel free to freak out at the sight of a drow though. It'll make for interesting roleplaying.