Can Xcode 6 and Xcode 5 coexist on the same computer?

I have them installed side by side right now and I have not encountered any problems with this arrangement. While I obviously haven't had Xcode 6 for very long, I have done the same thing with several previous Xcode beta releases as well and I have no reason to believe this release would be different.

EDIT: You can use xcode-select to switch between the different versions of the command line tools. From the man page:

When multiple Xcode applications are installed on a system (e.g. /Applications/Xcode.app, containing the latest Xcode, and /Applications/Xcode-DP.app containing a developer preview) use xcode-select --switch path/to/Xcode.app to specify the Xcode that you wish to use for command line developer tools.

The answer is YES

Where to download Xcode 6 beta

1. Go to https://developer.apple.com/xcode/downloads/
2. Select View on the iOS Dev Center
3. Sign in with your Apple Developer ID
4. In the top left, select iOS 8 Beta
5. Scroll down and search for Xcode 6 beta

The requirement for Xcode 6 is OS X Mavericks 10.9.3

It will install into /Applications folder with the name Xcode6-Beta, so it won't hurt your current Xcode

They can both coexist without any problems. You can set version that command line tools use with:

sudo xcode-select -s /Applications/Xcode6-Beta.app

Xcode 6 works on 10.9 too.