Q: Anyone know how to force Notes to sort alphabetically in El Capitan?

Yes, I too, would like to know when this feature will be fixed.

Looking through the forums, I see that this has been an issue for years.  Apple....  Please add the option to alphabetize!!   It should be a given that we can sort or notes in alphabetical order.  It's very disappointing to see so many people as for such a minor detail for years and not have it addressed

No one here from Apple. This is a user to user forum.

Try here: http://www.apple.com/feedback/