cidiemme:
I found this solution (https://www.kiwi-electronics.eu/blog?journal_blog_post_id=7):
Just like Yosemite, El Capitan requires kext driver signing. How this can be disabled in OSX 10.11 is changed however.
To get the CH340 drivers to work in El Capitan you need to use the new tool csrutil as follows:
Reboot and press CMD+R immediately after hearing the startup sound to boot to Recovery Mode
Open Terminal
Execute the following command: csrutil enable --without kext
RebootClaudio
Perfect, this worked for me. At first seemed nothing had changed but after unplugging and replugging nano clone /dev/cu.usbserial came back 
Thanks!