Changing XAMPP directory/file permissions
Instead of using an 'alias' at the Finder level, you might want to use the terminal to create a 'symlink'.
The command to do this is ln so you can learn more with man ln - but you can also check out these two articles that explain the concept a little clearer than the man page.

http://hints.macworld.com/article.php?story=2001110610290643
http://gigaom.com/2011/04/27/how-to-create-and-use-symlinks-on-a-mac/

To answer your other question, yes, everyone means EVERYONE, in addition to every user on the laptop.