Subversion doesn't track either the state or existence of working copies on the server, so there's no server overhead to keeping working copies around. Likewise, there's no need to let the server know that you're going to delete a working copy.

If you're likely to use a working copy again, there's nothing wrong with just leaving it on disk until you're ready to use it again, at which point all it takes is an svn update to bring it up to date and ready for use.

However, if you're definitely not going to use a working copy again, you can safely delete the entire thing, but you'd be well served to take a look through the working copy for unversioned files. To find these files, run svn status and review any files that are prefixed by a ? to make certain that they're not of importance. After you're done reviewing, you can safely delete your working copy.