I would try:
sudo find / -type d -name "postgis-2.0.0"
The . means search only in the current directory, it is best to search everything from root if you really don't know. Also, type -f means search for files, not folders. Adding
sudo allows it to search in all folders/subfolders.
Your syntax for
locate is correct, but you may have to run
first. For whatever reason, I never have good luck with
locate uses database of files and directories made by
updatedb. So if you have downloaded a new file there is more chance that your
updatedb has not updated the database of files and directories. You can use
sudo updatedb before using
locate utility program.
updatedb generally runs once a day by itself on linux systems.