vi /etc/yum/pluginconf.d/fastestmirror.conf
exclude=.hk,.cn
You could also use specific domains but as you can see above we are blacklisting all Hong Kong and Chinese mirrors in this example.
yum, blacklist, exclude, mirrorsvi, etc, pluginconf, fastestmirror, conf, hk, cn, domains, blacklisting, hong, kong, mirrors,