Getting the exact same problem as this as well
Although, I did notice a strange occurance.
I opened up the Notes App on my Mac, and it showed all the Notes I have made on my iPhone from when I first got it (May 09) till October last year, which is when I first got my Mac and must have sycned my notes from my iPhone to my Mac via iTunes (The 'oldschool' way as mentioned above)
However, I never remember seeing these notes on my Mac before this? (ie. When running OSX Lion).
I never used the Apple Mail App but could my notes somehow have been placed in there anyway from that one time sync?
I'm thinking about maybe going back in my time machine till before I installed Mountain Lion. Maybe even reveting back to Lion. Where in Mail did the notes live?
I'm thinking if I turn on Notes in iCloud on my Mac & then move these notes in Apple Mail from 'On My Mac' to my iCloud account, this will transistion all the notes to iCloud & I can just delete the notes on my phone, then turn on the 'Notes' option in iCloud settings on my iPhone & they will trickle back down again?
Really frustrating that Notes don't automatically transfer to your iCloud account when turned on for the iPhone. The same way Calenders & Contacts already do. Massive oversite apple...