It's a bumper. It's a grille. It's both!
Two more from the archives, again, I suspect, the Biblioteca Nacional José Martí Havana. They appear to have been taken in the early to mid-1950s; locations unknown. The commercial signs in the top photo – Zenith, Norge, Du Pont, Essolube – would have disappeared after the revolution, but in most other ways these scenes probably differ little from the present. In the lower photo, check out the 1950 Buick on the left with that year’s bold new “bumper grille.” Yikes!
If you would like to know more about Buicks of that era – and really, who wouldn’t? – here are two good sources: