There's usually a sidebar link to the chat of all SE 2.0 sites on the main/meta pages.
However, this link doesn't show up in the sidebar for public beta sites:
You can see this on Cognitive Sciences. For reference, the Meta Site does include the chat box.
Since the element is vertical there's really no harm in "wasting space", so I can't see why the chat link is excluded. While the space wasted is minimal, the chat box does make chat a lot more visible and lets you check if a site's chat is active as well.
Can Public Beta sites please get a chat box in the sidebar like all other sites? Chat is a great way to encourage "regulars" and deepen engagement between users, which is especially helpful for a growing community. Beta is one of the most important times for building community, so it seems extremely counterproductive to hide chat from Beta users.