I am using text for a printed document that will have English and then Spanish translation of the English. What is the best font combination?
When I am not sure about the languages that font supports I go to FontSquirrel and there you can see all languages that those free fonts support.
My recommendations are:
Source Sans Pro
You can follow this link and it will give you the list of fonts that support Spanish http://www.fontsquirrel.com/fonts/list/language/spanish