Darn you Shamus, you made me register just for this!
I wouldn't know a female Elcor if I saw one; with the way they speak, I'm not sure a human could tell without asking (or indelicately checking "under the hood".) Given how much more inclined the Elcor ambassador is to peace-making than the other ambassadors we see in the game, she may very well be a female Elcor. There were what, all of four Elcor in the game? Who knows if any were female?
The Salarians are, in fact, mostly male - and matriarchal, so their females are all back home running the Salarian empire. Although they look like salamanders, they probably should have been insects.
And while I'm also not sure I'd know a female Krogan if I saw one (they're reptilian, so mammaries are unlikely), given the genophage it would be unsurprising to me if the Krogan were a misogynistic patriarchal society that kept women locked away "somewhere safe".
But there is, in fact, no excuse for the Turians (I'll excuse the Hanar for having only three or four representatives in the game.) And it's actually kind of funny how much Liara tries to dispel the image of asari oversexuality when everything else in the game reinforces it. Yeah, I'm not buying it.