According to the VS 2012 (and MSDN Subscriptions) licensing document that can be found at http://www.microsoft.com/en-us/download/details.aspx?id=13350 you are allowed to install Visual Studio on just about any number of machines where you are the single user of the software. Quote from the license text:
"Where the Software Can be Installed and Run The licensed user can install and use the software on any number of devices. The software can be installed and used on your devices at work, at home, at school, and even on devices at a customer’s office or on dedicated hardware hosted by a 3rd party. However, the software is not licensed for use on 3rd party shared servers (“cloud” environments) or in production environments."