It might be better to create one the size that you want, then create outlines, and use step and repeat for the pattern.
ok, but I guess I do not understand how to add the "+" sign in to each individual box at one time. I have over 100 boxes that I want the "+" sign to be in at the same font size, color etc...
Unless I misunderstand your end result, what I was suggesting was to create one the way you like it, then convert that one into an object by selecting TYPE>CREATE OUTLINES. That will convert it to an object instead of type.
It would seem to be easier to create the repeating pattern by doing this instead of hundreds of text boxes.