I know the GOG store page says 14.04 is required but Steam and the Wasteland 2 forum said it would run on Ubuntu 12.04, but it's not working for me even though I installed all available upgrades for 12.04. I get a GLIBC needs to be >=2.17 error message when I run the startup.sh and I have learned that Ubuntu 12.04 uses version 2.15. Does anyone have any tips to get Wasteland 2 to run that don't involve upgrading to 14.04?

1) You can search for upgraded packages for 12.04, there's a good chance that they exist. You'd just have to know which repositories to use to upgrade them etc. I do not know exactly as I'm not an Ubuntu user.

2) If you have Steam installed, you could maybe use libraries in Steam runtime by symlinking to them (they're in ~/.steam/somewhere)

Chances are that the gog linux release version of wasteland 2 might work/might not work on ubuntu 12.04, depending on what hardcoded settings are in the startup.sh & other installer scripts.

Have you installed any development tools packages in your ubuntu 12.04 instance?
You probably already have them installed, but I had to ask that question.

The next step I would recommend is updating the source repository list your ubuntu 12.04 instance uses, lke Daliz suggested.
this link from the ubuntu support website will walk you through the process of adding source repositories to your ubuntu 12.04 instance. https://help.ubuntu.com/community/Repositories/Ubuntu

You will want to check what other software repositories ubuntu 12.04 users on the inxile WL2 forum are using.
off-hand, i have no idea what software repositories are required by the unity engine under ubuntu 12.04 linux.