I spent a pleasant Boxing-day afternnon assembling my duaghter's Petduino with her, but once finished and connected to my Macbook no port was available to connect to and download the software; despite having installed all the drivers.
The issue is apparently down to the way OSX El-Capitan validates the drivers it uses (they need to be signed), and the one linked to in the instructions is not signed and therefore wont be accepted by OSX, and as a result no port will be selectable.
I fixed this (goodle is my friend!) by using a signed driver for the CH340 Chip. The one i used i got from here - You might want to note this is the user manual.
Many thanks for a great product; both my daughter and i are looking forward to creating our own creatures!