As far as I know there is no simple way to rotate the text on your dimensions within one standard. However, if you go to Tools / Options / Document Properties / Detailing, you can change the dimensioning standard to change the appearance and position of the dimension text.
Changing the dimensioning standard still did not bring the desired result.
From what I gather, Ordinate dimension text is exempt from the given ANSI standard of all horizontally aligned text on a drawing.
Section 1.9 of AMSE Y14.5M does define and explain ordinate dims. I looked it up because I thought it was an actual rule to have verticle text for ords. However, there is not expressed statement about verticle or horizonal direction of text, but the one example does show verticle text along the x-axis. So, yes, it does appear to be the only exception rather than an expressed rule of its own.
