I've been emailing your relative Luis on and off for a few months, and his most recent email described his scenic trip to Spain, Portugal and the Basque country.
Luis did visit the hamlet of Guerena with his son and other relatives, but found no living Guerenas there, nor did he find any Guerenas buried in the local cemetary.
That said, he traveled as far south as Morocco, and as far west as south Portugal, up through Lisbon.
Luis hoped to find more family information in Alamos, Sonora which he plans on returning to in the near future.
The earliest Guerenas in Alamos that I am aware of are Modesto and Dolores Guerena (nee Chavez), and I presume your Carlos Guerena was their relative?
Modesto did meet my ancestor, Bartolome Almada, at the port of Mazatlan, Sinaloa, during the 1860's.
In the will of Dolores Guerena Chavez, she states that her eldest daughter-also named Dolores--married Jesus Marcelino Almada, my gggrandfather.
I considered the possibility of Jewish Guerenas because I wanted to look at the history of the Guerena name from all angles, but if one looks at medieval Basque history under Castillian dominance, one finds Sephardic Jews strictly segregated from Christians, to the extent that few Basque surnames such as Guerena grew Sephardic branches.
Also, in some families, there are oral histories indicating that a remote ancestor was pressured to leave his or her homeland due to religious intolerance; I do not believe this applies to either the Guerena or Almada families.
There is a historical footnote in Almada family history wherein an Almada ran afoul of the Inquisition in New Spain; did the same thing happen to the Guerenas?
Thanks again for your reponse Tom; please take care!