I'm with everyone else. Text in the sheet drawing and not the XREF. Could be Model Space or Paper space. I won't get into that argument. Let's save that for another thread (not like there haven't already been a thousand of them).
Matt Kolberg Cansel - Autodesk Division http://www.cansel.ca/
If you want to do your whole project in one file (not recommended) you would want layer states for each. This would require viewport layer control and annotation layers per discipline (for lack of a better word).
I would suggest at a minimum use xrefs and one file per discipline.
Joseph D. Bouza, P.E. (one of 'THOSE' People) Civil 3D 2012 & 2013 HP Z210 Workstation Intel Xeon CPU E31240 @ 3.30 Hz 12 GB Ram
Note: Its all Resistentialism, so keep calm and carry on