Hi Hobbit_Fan,
somewhere (probably UT or HoME) I read that the Numenoreans had 'mixed' with the local population. This isn't so surprising, as so did the Numenoreans in Gondor. I'd guess though that the ruling elite likely aimed to retain their Numenorean er, 'purity'.
Remember that they likely included descendents of the Second Age 'King's Men' and the defeated remnant of Gondorians from the Kinslaying era. I'd imagine them as highly racist, since the Kinslaying was caused by 'dilution' of Numenorean blood by the Northmen, in part. But a lot can go in in those long millenia.