Civilizations in star clusters

Star clusters contain hundreds to thousands of stars in a very small
volume. The stellar density of open clusters averages 1.5star/ cubic
light years whereas in the region of our sun it is about .1 star/cubic
light year. This means that interstellar travel within an open cluster
would be much easier than without. Globular clusters have much higher
stellar densities but generally contain very old stars and they are so
close that stable planets might be difficult. However, if a
civilization did arise in a globular cluster, you would expect it to
rapidly colonize the entire cluster, if there were any stable planets
worth doing so.
A civilization within a star cluster might have an entirely different
perspective on astronomy than we do because their sky would be filled
with so many stars that night would be nearly as bright as day. They
could be expected to rapidly find planets around the other very close
stars. However, once a civilization did fill such a cluster, it would
expand much more slowly because outside the cluster the stellar density
falls so that distances become extreme. Even worse, many globular
clusters are outside the plane of the Milky Way so that distances to
stars outside the cluster are much greater than around our sun.
SETI might emphasize looking at star clusters rather than individual
stars.