I'm in the process of revamping my Simcity Saga, because I could already see myself getting bored trying to play out the families in real-time. So I wiped the neighborhood and am starting from scratch. In doing so, I decided to use a tutorial I found on merging neighborhoods, rather than recreating them.
Now, I am constantly going back and forth, reinstalling whatever neighborhood I'm working with. I basically needed two copies of the default towns; one for merging and wiping characters and starting fresh with houses, roads, and decorations intact; and one for cloning/recreating characters in SimPE/Bodyshop. Only way to do this is to renumber each neighborhood and ALL the files within it that refer to that number (i.e. N001 becomes N100, and all zillion-odd files within it).
So I found this tutorial and program. I tested it and I now have 2 identical copies of Pleasantview on my computer! The only thing that didn't translate was the neighborhood story, which is an easy enough copy/paste job if I need it. I'm going to copy the rest of the hoods and then attempt the merge and report back!
Here's the link to the renumbering hoods tutorial:
Clicky! The program you need is linked a couple of posts into that thread.