Daryl posted a good tip for placing model text on a curved wall. While it is a creative solution I believe I have a better method for you all.
First off create a new family from the Generic Model – Face Based template. Put in a piece of model text, give the model text an instance parameter so you can change it in the project, you can also give parameters for material and depth. Load this into your project and place on the face of the wall (which can be done in plan, elevation or 3d)
Now in plan view array some ref planes around the center point of the wall to get your spacing between the letters correct, to align these just select and drag to align with the ref plane, you cannot use the align tool. Now if the wall ever changes the text will go along with it.