I know this a really old post, not sure if you still come on this site. But I am researching my husband's Portuguese family. Their name was Sylva / Silva /Sylvia/ Silvia / da Silva. They settled in New Bedford, MA. I found several on the 1855 MA census. Let me know if any of these names/dates ring a bell.
John b. 1815, Portugal
Mary b. 1825, Portugal
Mary J b. 1845, Massachusetts
Joseph b. 1845, Massachusetts
George b. 1855, Massachusetts
John Jr. b. 1850, Massachusetts
Antone b. 1845, Massachusetts
Lousia b. 1805 Portugal
In this census they were listed as Sylvia, later on I mostly see them as Silva or Sylva.
I'd love to hear about your New Beford Da silva family.