I really haven't tried this, but from reading several Ubuntu and Linux books, I can say:
You should be able to use a shared /home partition across Ubuntu distributions, providing that your login password is the same on both
Also, I would recommend that you move your home directory to its own partition, just in case you run out of space, or if you want to share it with another Linux distribution.
Also I would recommend using eCryptfs because, it guides you through the steps needed to create a private and secure encrypted directory.
To install eCryptfs, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the commands below:
sudo apt-get install ecryptfs-utils
Or you can download it Here.
For information and examples that might help you accomplish this, you can click Here for more details. Hope this can help.