I have squirrel problems too. What I've started to do is put a layer of decorative rocks on the surface of the soil, and spray the sides of the fabric pot with neem oil (they hate the scent of it).
The rocks are $5 at Home Despot up here in Ontario, and one bag covered the surface of two 7 gallon pots, and a 60 litre tote, with a little left over.
This is the first year I haven't had the little bastards digging in my pots, and the neem is keeping them from chewing holes in the sides of the fabric pots.
I'm still having trouble getting these pics to show up full size instead of thumbnails.