In Budgie 10.4 release, there is a stand alone settings application for Budgie Desktop. It provides option to set the visibility of panels.
See automatically hide option in Budgie Settings
Ubuntu Budgie 17.04 comes with Budgie Desktop 10.2.9. You can update to Budgie Desktop 10.4 using backports repository provided by Ubuntu Budgie team.
In command line, it can be done as follows:
sudo add-apt-repository ppa:ubuntubudgie/backports
sudo apt update
sudo apt install budgie-desktop
For more on installation of Budgie 10.4 on Ubuntu 16.04/16.10 and 17.04 see original blog post shared by Ubuntu Budgie team.