Easily install ALL of Google's Web Fonts using the following command in your terminal.
curl https://raw.githubusercontent.com/qrpike/Web-Font-Load/master/install.sh | bash
To update the fonts, just re-run this script. It will overwrite duplicates.
You may need to restart for Font Book to pick up the new fonts.
When using this script, it installs A LOT of ( ~1660 ) fonts. You may have to disable "Font Preview" in Photoshop.
curl https://raw.githubusercontent.com/qrpike/Web-Font-Load/master/uninstall.sh | bash