If you constantly are being reminded to install software updates you don't really want to install, you can right-click (Control+click) the name of the update and hide it, eliminating the reminder.
[crarko adds: I think this is probably known already to many of you, but if it's not it can be a handy trick. I find the whole App Store method for Software Update a lot less pleasant than the old Snow Leopard mechanism where it was separate, but maybe I'm just old fashioned.]

