Forget Paisley, you can go to some God awful places like Banff and a good 60-70% of football supporters there will follow one of the Old Firm.
I've lived in the central belt of Scotland for 15 years and I can honestly tell you that apart from actually going to the grounds and sitting next to the poor bastards, I have NEVER met a fan of Stirling Albion, Alloa Athletic, Stenhousemuir (Paddy aside) or East Stirlingshire. I know 2 Falkirk fans and one of them is a Wolves fan who randomly picked Falkirk as his second team.
In Stirling where I used to work there are two main council estates, The Raploch and The Cornton. Cornton is mainly Rangers and Raploch is Celtic. Even where my parents live in Dunblane which is a quaint little commuters town, there are three main pubs; the Tappit Hen which is a whiskey/real ale pub (cracking boozer actually), the Village Inn (Celtic) and the Dunblane Hotel (Rangers).
The only places where you'll find more football supporters supporting their local team rather than the Old Firm are Edinburgh, Dundee and Aberdeen and even then it's a close run thing.