Excited to hear you are interested in teaching CS Discoveries! The whole course is now published and all available. You can check out the overview of all the units and links to the lesson plans and materials at code.org/csd. The course is in fact meant to be two semesters so that a school can teach a 1 semester class and just use the first semester content. So if you are planning on teaching as just one semester our recommendation is to use Units 1 to 3 (the first semester of the course).
Hope that helps!
Dani
CS Discoveries Team