We study the geometrical commensurability oscillations imposed on the resistivity of 2D electrons in a perpendicular magnetic field by a propagating surface acoustic wave (SAW). We show that, for ω<ωc, this effect contains an anisotropic dynamical classical contribution increasing the resistivity and a nonequilibrium quantum contribution isotropically decreasing the resistivity, and we predict zero-resistance states associated with geometrical commensurability at large SAW amplitude.