When activating WordPressMU should I wait until the site is live?

I am brand new to WordPress but I have about a dozen Joomla sites on the go. I am thinking of switching some of them to WordPress just because it is easier for users.
I am setting up a multi site install for myself but I already have multiple sites set up for my URL on one Joomla install, it is working fine, so this is just a test site which is in a sub-folder. I want to set up the WP multi-site, see if it suits me, and if it does, then I'll move it to my root folder to make it live (that's how I do it with Joomla).
I don't have a problem activating the multi-site, I'm familiar with .htaccess and know enough about PHP that I can copy code to the right place but will doing so make my test site live?