I'm currently having a genre dilemma of my own, so I'll raise it here also (sorry for the intrusion, HopelessDreamer

). Are dystopias set in the future considered science fiction rather than mainstream? My WIP is set in the future, but doesn't have much of a technological focus. Is
The Children of Men considered science fiction? What about
1984?
Brave New World? Obviously bookstores are more likely to place such famous works under general "fiction"--but for a first time novelist querying an agent (in theory--I'm not nearly to that stage yet!), would the novel be considered science fiction, or mainstream?
I'm in the same spot as you, except that I've already finished my dystopian novel and am querying agents about it.
My query letter opens, "Default Line is a dystopian novel (not science fiction) that takes place in 2048."
I think the dystops you mention have to be considered separate from sci-fi, because they just aren't sci-fi. They're social novels. They're about what people do to each other, not what affect technology has on us, and the technology they include is never ground-breaking (TV was over ten years old when Orwell wrote 1984).
I'm specifically not querying agents who handle sci-fi, because (a) they might not be interested or be disappointed that it isn't "real" sci-fi, and (2) I'm looking for a bigger audience than the sci-fi genre appeals to.
But it really does pose a problem. I have some violence, some suspense, some intrigue and some sex, but my novel is neither thriller, mystery, nor any other genre I know of.
And by the way, no, Children of Men isn't sci-fi. It would have to include some scientific reason for the sterility, complete with some race to find a cure, to be sci-fi.
Nor is 1984. Brave New World qualifies as sci-fi, but has readership beyond the genre, which is why you won't see it in sci-fi sections in bookstores.
Also not sci-fi are The Handmaiden's Tale and the Michael Palin movie, Brazil.