I'm thinking of the population densities in my campaign, as not all areas have the same fertility.
The Elven Confederation, for example, is mostly forested and has quite a low population density; I'd say about 25 Elves/square mile (150 families per 6-mile hex or 2,500 families per 24-mile hex). The same goes for the mostly Steppe-Forest Principality of Tagorsk.
The mountainous Dwergerhold and Dwergerberg, for example, are mostly mountains and have quite a low rural population density, but, on the other hand, they're quite urban; so I'd say about 40 Dwarves/square mile (250 families per 6-mile hex or 4,000 families per 24-mile hex).
The Three Principalities (Norokh, Vorkono and Gironov) are the breadbasket of the region, with a population density of 80 people per square mile (500 families per 6-mile hex; 8,000 families per 24-mile hex).
The Two City-States of Zagadur (Igorgrad and Shakhtar) contain mostly mountainous terrain and forests, with some arable land, so their population density would be 50 people per square mile (300 families per 6-mile hex; 5,000 families per 24-mile hex).