Sapucaia do Sul is in Grande Porto Alegre.
Locals call it the TRENSURB. You can take the train from the airport to many stops in Sapucaia do Sul and to cities beyond (Porto Alegre, Canoas, Esteio, São Leopoldo and Novo Hamburgo). The fare is R$1.70 and there's a station near the Porto Alegre Rodoviaria (central bus station) and Porto Alegre Salgado Filho airport. It is more or less safe to walk during day time from Rodoviaria or the airport to the stations.
2nd-order administrative division
Primary administrative division