Well yes. Did one this week locally, despite the book not being available in UK other than in this local bookshop. Why bother? Because it's important to keep your profile out there. You need people to know who you are, and what you do.
You may think, if you are unpublished, that this doesn't matter. But honestly, the sooner you start building a profile, the better. Obviously you can't do a book signing, if you haven't got a book. You can, though, let people around you know you're a writer. I've been doing it for years and amazingly, there are still people who know me well who don't know I write. "Oh, you've written a book?" they say. Er - yes, actually, quite a few..
Don't let the unpublished ticket stop you from saying what you do. You write, therefore you are a writer. A writer writes. It doesn't say, a writer is only a writer when published.
For the record, only one stranger bought a book. Everyone else that came was someone I knew and had told about the signing. That doesn't matter. My profile in the town has risen by that much - other people came into the shop during the signing, plus the books are still in there along with a huge poster of the cover. This is promotion.