As mentioned by The Loop, the public beta of OS X Yosemite will be released on Thursday, July 24th. The release will be the same build released to developers on Monday. However, the developer version of the OS will be updated more often over the next few months than the public beta will be.
The official release version of OS X Yosemite will be released later this year, likely in the October timeframe. The public beta will be limited to the first one million users to sign up on Apple’s site.
It is highly recommended that if you plan on participating in the public Yosemite beta, that you do so using a secondary Mac computer. While the current OS X Yosemite release is stable, and runs well, it is a pre-release version of software, and there always exists the possibility of data loss.