About Estu Preta
First question everybody has is "What does Estu Preta means?". The answer to that is a long story, but in the end a simple one.
Also if you want to use a secret language in your patrol you should all set to work to learn "Esperanto".
It is not difficult, and is taught in a little book costing one penny.
This language is being used in all countries so that you would be able to get on it abroad now.
In the book with which Lord Baden Powell started Scouting he suggested that every Scout should learn Esperanto to use in all countries of the world as a 'secret' Scouting language. This is commonly not used and there are most likely a lot of Scouts that do not know Esperanto these days.
The official Scouting motto is Be prepared!. This is being used all over the world by all Scouts. The idea from back in 1907 has changed over the years into being ready to do what has to be done together with your fellow Scouts.
Esperanto + Be prepared! = Estu Preta
And to make a long story short, 'Be prepared' in Esperanto is 'Estu Preta'