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I ended up simply using an encrypted sparsebundle on the Mac and putting my Evernote folder in there. The system would then automatically mount it whenever I logon, as Evernote always runs anyway. So the only way somebody could locally access my Evernote data is by knowing my Mac OS X password, if they don’t, the encrypted sparsebundle will be locked.

Of course there’s still the possiblity of somebody cracking the Evernote account password and viewing all the unencrypted notes online, but I don’t think that’s too likely. Besides, I don’t have any sensitive information stored in Evernote (except plain text, which is then further encrypted within Evernote). Documents etc. are scanned to 1Password which encrypts everything and doesn’t store it unencrypted anywhere.