While installing the ISO yesterday for a daily test on Xubuntu 13.04, I learned that an ethernet cable had gone bad. The laptop then tried to connect to wi-fi during the installation. However, it did not attempt to connect until after the screen that asks me to make sure I'm connected to the internet in order to download updates during the installation. After I connected to the wireless router, it did go back to that screen and gave me the opportunity to check the box to download updates. As a suggestion, I would have the installer prompt the user to connect to wi-fi before presenting the option to download updates. In other words, when the only NIC available is a wireless NIC, the screen called "Wireless" should come before the screen called "Preparing to Install Xubuntu".
This release of Ubuntu is no longer receiving maintenance updates. If this is still an issue on a maintained version of Ubuntu please let us know.