Of course 2.18-beta is findable. What we don't want is a bunch of people getting it, whining about bugs on Head-fi, and making people confused. It's already happened. Search through the thread. People have been confusing beta firmware bugs with stable firmware bugs. The simplest and best way to get the beta firmware is to PM chow and ask to join the beta testing group.
I don't know if any of you have an iPhone, iPad, or iPod Touch, but everytime a new beta is released, the number of people leaving negative feedback in the appstore because the apps crash on a beta firmware version thousandfold.
Don't be these people. Just wait for a stable release, or join the beta group to actually help make it stable.