The best place to avoid water is right over by the sun/hubcap fountain right across from Playhouse Disney. That's right by the parade start point, so I think the water cannons aren't really firing yet as the parade comes out there.
I don't think they use the water cannons much in the cooler weather as I saw it last week and there was no water during the parade. The only bubbles I saw were during the Nemo portion of the parade.