That some Arroyos have Sephardic Jewish ancestry is doubtless. Sephardim.com records Arroyos in the history of sephardic Jewry. Arroyos are found in the book, "A Life of Menasseh Ben Israel", by Cecil Roth. This book contains names from the Sephardic community of greater Amsterdam. Amsterdam was a major haven and transfer point for Sephardim and Morranos leaving Iberia.
Arroyos are also found in the book, "Crisis and Creativity in the Sephardic World: 1391-1648", by Gampel. This book lists Sephardic movers and shakers during the period.

However to come to the conclusion that all or even most Arroyos have Sephardic jewish roots is doubful in my mind. Here is my reason why I believe that assumption is improbable. That site records hundreds of surnames including the following common Spanish names as having Sephardic members: Aguilar, Aguirre, Arias, Acevedo, Caravallo, Carrion, Diaz, Enriquez, Escobar, Falcon, Fernandez, Figueroa, Fuentes, Gonzales, Lopez, Martinez, Melendez, Mendez, Nunez, Perez, Quinones, Ramirez, Rios, Rivera, Rodriguez, Rosa, Suarez, Torres, Vasquez Vega. Unless the names are of clear Hebrew origin I would doubt Sephardic origins to all these Hispanics. What do you thinks?