Rebecca Greason's guide is over 10 years old, but you still find more basic information in certain areas than you'll find in Santi's guide. She lists one "Un Pequeno Libro De Oro" title dated 1959, with a price range of $5-14. Bottom line, it's worth what an interested collector will pay for it. If you're going to auction it on eBay, you might start it at $8-10 and see if it sells/if it climbs higher.
I recently purchased a Little Golden Book that is written entirely in Spanish. The copyright is marzo de 1959 by Editorial Novaro-Mexico S.A. It is titled "Cuando Yo Sea Grande" (When I Grow Up - in English) I would say it is in excellent condition. The pages are white, not yellowed. No tears or writing other than in the name box on the front cover. There is a little wear on the corners of the cover, but the binding is tight.
My Spanish is not so great, but I think it says that it is the first edition, 30,000 produced in March of 1959.
I cannot find anything in any of the books/articles on collecting LGB about these one that were produced for Mexico. Any help you can give me in finding a value for it would be greatly appreciated. Thanks!
Amkara