I think at this time the beta version is only available to developers (app programmers). You have to register to be one of those.
Personally I would not download it just to try to be ahead of the curve. I don't do any updates until a version is out of beta and even then I usually wait a sub-version or two until others like you have done all the bug discovery for me. ;-) Remember that betas can potentially cause problems and you should only run them on devices where you don't care what could happen to your data (i.e., you have a second iPhone or whatever, and maybe even have a different Apple Account for testing).
Uh, I think the general guideline is if you don't know all this already then you should not be running any beta software. ;-)