>>>I enjoyed the spelling of his name in the reference you gave me - João Rodrigues Cabrilho. As is so typical of history things become distorted. I would like to know why we were taught the Castellano spelling? He is a very famous person in California History. We even have streets named after him - with the Castellano spelling.
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>>To be honest, Juan Rodríguez Cabrillo is closer to ancient portuguese spelling: in 17th-18th century portuguese (I'm not at ease with previous periods) the most common spelling would be something like Joam Rodriguez Cabrillo. The use of the tilde to nasalize phonemes is a modern solution.
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>Could there have been a less clear separation between Spanish and Portuguese back then? Was there greater use of dialects that were somewhere in between, such as Galician?

Yes, portuguese and spanish ("castellano") were much more alike during the Middle Ages - and it was not uncommon to see portuguese authors writing in spanish or something really close to spanish even after that period.

The exact place of Galician in respect to Portuguese and Spanish languages is a matter of debate - and a rapidly evolving one. Besides, it raises delicate social, cultural and political issues and so it's far from being a pure linguistic question (if there is one). But, frankly, I'm not very comfortable with this (I took a "side", but it's kind of emotional, not based on ground knowledge).

>I looked at a Galician dictionary in a bookstore and couldn't decide how different it looked from Spanish or Portuguese, especially since I don't know either. To me the spelling of the words looked more like Spanish, which makes sense since Galicia is in Spain.

I think there are several graphical forms of Galician, but they tend to be closer to Portuguese. A link to follow: http://www.orbilat.com/Modern_Romance/index.html. And Çopyright, an online publication that I believe to be well balanced in this respect: http://www.udc.es/dep/lx/cac/sopirrait/indice00.htm.