Grândola is a good choice, though because of the political association it will never be a hit with the non-leftist crowd. Dunas or A minha casinha are probably more popular/neutral choices and, unlike Zeca's song, no-one outside of Portugal has ever heard about them (Grândola is well-known amongst at least some niche circles in Spain, where it was first released/sung during the dictatorship).

OTOH I'm fairly sure that in 50 years few will remember Xutos and GNR, while Grândola will still be sung over the centennial celebrations (assuming we don't fall back into a far-right dictatorship by then...)