They are specially annoying when I need to upload to the server a web solution.
Is there a way of configuring SVN to create the _svn folders outside my working directory
It's not (currently) possible to configure SVN (or TortoiseSVN) to create the .svn (or _svn) directories outside the working copy. I believe that the SVN 1.6 roadmap includes revisiting the working-copy library. The ability to put the administrative directories somewhere else might come out of this work, but I'm speculating.
You should use the "svn export" command to create a "clean" copy of your working copy (i.e. without the _svn directories). This works from the command line client.
If you're using TortoiseSVN, you can right-click on the working copy, and choose "Export...". This will ask you for a folder to export the files to. Alternatively, you can right-drag a working copy to a folder (one that's not a working copy), and TortoiseSVN will bring up a context menu; among the options are "SVN Export to here" and "SVN Export all to here", the latter also exporting files not under version control.