Estan haciendo obras en la calle
In this sentence does obras mean work or works, or does "obra" and "obras" both just mean work. Also can "obras" be used to mean workers in a different situation.
2 Answers
Yes. Obras means construction or repair work on the street.
Obra -- a masterpiece (obra maestra), a theater piece (obra de teatro), work or production (la obra de Picasso, de Neruda, etc.)
Obras -- alone it almost always means public works (El Ministerio de Obras Públicas or The Department of Public Works). However, depending on the context it could be a collection of literally works, paintings, etc.
I think it is "They are doing work (projects/construction) in the street.
By the way the people doing the work are obreros/as.