From the information we have so far, evil-aligned creatures are very rare. If I'm not mistaken, all we have so far are demons, devils, and one blood of vol cult member.
Thus, I expect only very few, if any, evil-aligned elemental creatures. If the City of Brass is really such a big deal, then it can be assumed that even Efreeti aren't out to murder the PCs. Though they surely wouldn't mind much, if there is enough to gain.
And given that metallic dragons are not automatically benevolent anymore, I'd except no good-aligned elementals whatsoever. Infact, I'd be quite suprised if there are many good-aligned creatures to begin with. Perhaps only the angels. That way, the combat stats of nearly every creature in the Monster Manual can be used.