Should you use Debian testing?

To get the most updated packages but still have a usable system, you should use testing. Unstable should be used only by developers and people who like to contribute in Debian by testing the quality and stability of packages, fixing bugs, etc.

Is Debian testing unsafe?

Is Debian unsafe in the aspect of security because it uses rather old software versions? No, that makes it more safe, because those versions have been out there long enough for the bugs (of all kinds) to have been found and fixed. Understand this: it is NEW software that is unsafe, not old software.