^^^Happens a lot. There's a guy in my neighborhood who put in huge palm trees and giant birds of paradise and is fighting with the HoA about it now. They want him to remove them as they are specifically listed in the landscaping guidelines as non applicable for "trees".
There are other folks who want to put in Canary island palms and got shot down:
as bones mentioned - you probably should take a drive around and see what others in your neighborhood have done to create privacy as well as discussing it here with other residents of your neigborhood.