Same problem here. Resorted to keeping everything plain text after trying so many half-baked and sticky note taking apps that prevent your notes from being ported.

Currently using this Chrome extension: https://chrome.google.com/webstore/detail/marcador/nneoamjib...

Started as just adding bookmarks to your Dropbox, but now it lets you add plain text notes.

And it only has access to its own app directory--not your whole Dropbox!