It's possible that the answer to this question is "no." Justice Benjamin Cardozo was a descendant of Spanish or Portuguese Jews who immigrated to America, and took great pride in his Sephardic Jewish identity. For details, see Andrew Kaufman's excellent biography of Cardozo.

That said, ethnic identity is largely a social construct. So I can understand if Hispanics today take special pride in Sotomayor's appointment because she would be the first justice whose parents were recent arrivals from Latin America. Like many racial or ethnic classifications, "Hispanic" is a somewhat arbitrary label. It includes widely divergent groups such as Brazilians and Mexicans, while sometimes being used in a way that excludes Spanish and Portuguese immigrants and their descendants (including Cardozo). That does not mean, however, that the term is completely incoherent. US Hispanics do have a distinct identity of sorts - even if only because American society has historically defined them as such over the last several decades.