We have previously seen the installation of Android SDK (Revision 17) on Ubuntu, you can check it here. Another version (Revision 20) is now available, which we will help you install it via PPA on Ubuntu 12.04 and Linux Mint 13.
The Android SDK folder will be in the home directory as show in the SDK Path in the main interface of the application. To install the ADT Plugin, you can find instructions in the link provided above.
Android SDK Manager (R20) Installation
To install Android SDK Manager on Ubuntu 12.04/11.10 or Linux Mint 13 (Maya), open the terminal and run the following commands (i386 systems):
sudo add-apt-repository ppa:upubuntu-com/sdk
sudo apt-get update
sudo apt-get install android-sdk
Start now Android SDK from the Unity dash:
Here is a snapshot of Android 4.1 (Jelly Bean) started with Android SDK Manager: