The installer disc also has a Live Environment. This allow you to try Ubuntu, without installing it. All you need to do is download the iso image from here, and follow the guide here to create a bootable USB stick, or here to burn to a DVD.
Then all you need to is select in 'Boot Device Selection' to boot from the DVD/USB stick, and it'll work. Yet another guide on selecting it to boot from is here
There are some other helpful things here:
The only things you need to be aware of is some hardware drivers, mainly for wifi or graphics. You can get some of these drivers, and proprietary audio/video codecs required to play media, by allowing 3rd Party Software to be installed, if you do try to install it.
Hope this helps, and enjoy Ubuntu!