FYI you can use the techniques mentioned here to get ubuntu working on your MBP 6,2 using only the integrated GPU:
http://forums.fedoraforum.org/showpost.php?p=1664873&postcount=10
Here are the steps I took, adapted from there:
edit /etc/default/grub and add the following line:
GRUB_PRELOAD_MODULES="iorw"