I believe much of the Ancient writing that we see in Atlantis (and possibly in Stargate once the Atlantis series began running concurrently) can be translated to english.  To make the translations we have the ancient to english dictionary:

[![Ancient to English translator][3]][3]


First, the Atlantis gateroom:
[![Atlantis Gateroom][1]][1]

> We hold these as the truth
> 
> A hearty welcome to those of other worlds
> 
> Visiting our home for the first time welcome again
> 
> To those returning you have been gone too long and your
>
> Absence has weighed heavily on our souls we are
> 
> Whole again that you are among us and we celebrate you being here
> again
> 
> As we leave for distant worlds we pledge to respect the lands of
>
> Our neighbours and to act with integrity as ambassadors in peace time
> 
> Of our people travellers with open hearts will always be welcome
> refugees
> 
> From tyranny may seek shelter under our roof and our people will lay
> 
> Down their lives to protect the weak and the just let this be our
> pledge to those
> 
> Inhabitants of this world and all we may ever know we will always
> strive to
>
> Come in peace as we go in peace and you will be welcome on our shores
> forevermore


We also have the following image from the Season 1 episode, *Before I sleep*.  The writing on the zero point module station (at the bottom of the picture) translates.

[![Before I sleep][2]][2]

>STAY CLEAR

  [1]: https://i.sstatic.net/kUE82.jpg
  [2]: https://i.sstatic.net/GXNzh.jpg
  [3]: https://i.sstatic.net/NoDCw.png