Can you debug from Visual Studio 2012 directly to Microsoft Surface (or any Windows 8 RT tablet)?

Yes, Visual Studio remote debugging supports debugging an app running on an ARM target. You can find more information "What you need to know about developing for Windows on ARM (WOA)."

Visual Studio has the remote debugging tools for working with external devices and other computers. In a Windows Store application project you go to the project properties and click the debug tab. Choose the target device in the dropdown Debug settings (click to see screenshot)

You'll need the setup remote debug service on your tablet and on your dev computer. The devices need to be on the same network subnet. I'm not sure how that will work on the Surface ARM device, as they cannot join a domain. I guess we'll know more once the hardware ships.

Get your remote debugging tools at Visual Studio Downloads.

Jason Zander has a post about working with ARM devices that might be helpful.