The effects of disorder and valley polarization in graphene are investigated in the quantum Hall regime. We find anomalous localization properties for the lowest Landau level (LL), where disorder can induce wave function delocalization (instead of localization), both for white-noise and Gaussian-correlated disorders. We quantitatively identify the contribution of each sublattice to wave function amplitudes. Following the valley (sublattice) polarization of states within LLs for increasing disorder we show the following: (i) valley mixing in the lowest LL is the main effect behind the observed anomalous localization properties, (ii) the polarization suppression with increasing disorder depends on the localization for the white-noise model, while, (iii) the disorder induces a partial polarization in the higher Landau levels for both disorder models.