READ ALL OF THIS BEFORE YOU ATTEMPT ANYTHING! If you lose any data, I'm sorry, but you're getting what you paid for and it worked for me, so I can't help you.
The problem, at least for me and apparently for a lot of us, is that my notes date back to 2009 and were created before iCloud existed. They defaulted to being created On My iPhone, and nothing existed to port them through the iCloud so they would be backed up. I went to the Apple Store in El Paso on Monday and spent half an hour with a Genius, we fiddled and finally concluded that you can't get there from here. The only solution seems to be to re-create all Notes that you want backed up via iCloud. I do not consider this acceptable, but what can you do?
I found the easiest way to do this was on my iPhone, it was faster with my thumb than it was with my trackpad on my laptop, at least for me. Your mileage may vary. I'm sure a clever person could write a macro or script to do it, but I knew it would take me longer to write and debug such a thing than to do it manually. So here are my steps:
- On your iPhone, go to Settings/iCloud. Make sure you're signed in, make sure Notes is turned on.
- Still in Settings, make sure your Notes settings are to Default Account iCloud
- Open Notes, Scroll down to oldest note, open it.
- Select All, Copy, + (create new note), Paste, Done.
- You should still be at the bottom of your list, delete the old note that you just copied.
- Go to step 3. Rinse, repeat. Stop when you get to Notes dated today. By starting with the bottom of the list, your Notes should still be in chronological sequence.
BEFORE YOU DO THIS, create a couple of Notes with the iCloud settings turned on to make sure your account is working and everything is flowing through. If it isn't, then I don't know what to recommend but I wouldn't go through with this.
When you're done, on your phone open Notes, click Accounts, and click On My iPhone. It should be blank. Anything left there might need to be recreated for iCloud. Open Notes on your computer and click the iCloud tab and verify all your notes are there.
It took me just over an hour to review and copy 140 notes dating back to 2009, I deleted about 20 along the way that were either dupes or no longer needed.
In my case, I had only changed or created about a dozen Notes since upgrading to 10.8, and my phone was backed up to my laptop about a week before I did the upgrade, so the copies that I have are reasonably fresh in case I screwed something up.