Dear David,
to plot a filled contour plot with lines at 0, 0.5, 1, 1.25, 1.5 one has the command
plotpdf(SantaFe,Miller(1,0,0),'contourf',[0, 0.5, 1, 1.25, 1.5])
analogously you can have pure contour plots using
plotpdf(SantaFe,Miller(1,0,0),'contour',[0, 0.5, 1, 1.25, 1.5])
Plotting contour levels on top of an smooth plot is not supported by MTEX 3.3 but will be possible in MTEX 3.4
Ralf.