Not sure. I guess...as a workaround...it could be possible to encrypt all of the text on a single note. That's not as elegant as the ability to simply encrypt a note (at the note level, instead of the content/text level). Others have suggested using the "Saferoom" product, but i'm not really interested right now in bringing in more integrated products with Evernote.
I'd like to be able to encrypt an entire note, as well as maintain the current capability to encrypt specific text within a note. In the way I'd like to use Evernote, I want to create a secure note into which I'll add related content. I'd like that entire note to be encrypted.