Text objects on a map are the same as any other text object. You can change the fontsize of the text object once you have the object handle using the SET function.
The following method extracts all text objects in the current figure that have a non-empty string, and changes their fontsize:
figure; axesm miller
framem('FEdgeColor','red')
textm(60,90,'hello')
textm(50,90,'hello')
textm(40,90,'hello')
textm(30,90,'hello')
h = findall(gca, 'type', 'text');
h_string = get(h, 'string');
index = find(~strcmp(h_string, ''))
h_new = h(index);
set(h_new, 'fontsize', 17)
Note: this may also change the fontsize of axis labels if they already contain strings. The XLABEL, YLABEL, and ZLABEL are text objects which are children of the axes.
