A Big 12 Country sign on I15, I80, 4th South, Wasatch Boulevard, Bangerter, Pioneer Crossing, etc., would not bother me a bit.
Banners in town on streets. Sure, why not. Get political. Make SLC do it - I know, they won't.
I just bought a boat, 2 jet skis, 2 Yamaha Rhinos, and a Kawasaki Teryx. All used of course - I am cheap. But, I do not know if I could bring myself to plaster them with any stickers - same for my truck or SUV.
Flag in the yard - sure.