Thanks Eric, It sounds like the best I could do (certain zoom settings and small font) might be acceptable.
I've just had a play with Excel Map. Could be useful in some circumstances, but I couldn't work out how to plot data keyed on Texas Counties...
Now it looks like the resulting map is going to be reproduced in print, so we have to make it monochrome. Might have to use a paint program to substitute colours. Good thing it is a one-off job
(buying MapInfo would be too much for a one-off like this)
Richard