If installing Ubuntu with the idea that Orca will be used extensively when it's up and running, don't waste time with Xubuntu, or any other 'light weight' distribution: Orca must have Gnome installed, so just get to it, with regular Ubuntu or whatever, and avoid any that don't install Gnome.
Linux Journal Orca article:
http://www.linuxjournal.com/article/9978
from the March 2008 issue, no. 167
Project site(?):
Run from the command line:
orca --text-setup
As I recall, this will require setting up some speech synthesis, but the mode can be changed once Orca is running and you are in the GUI environment, and reconfigure there. Once there you can adjust to use the Braille monitor (BrlTTY) or the magnifier application (gnome-mag).
The default "Orca Key" that prefixes most Orca hotkey sequences:
desktop computer - Insert key
laptop computer - Caps lock key
I'll abreviate "Orca Key" as OK.
To get to configuration settings when in Gnome, OK-space, that is Orca-key and spacebar.
You can start Orca when in Gnome by using the 'Run Application' dialog box, frequently opened with Alt-F2 keys, and filling in 'orca' on that.
(Do not put anything below this line)