Have ridden lots of places and organized rides with basketball shorts or baseball pants and a t-shirt, don't much if I look out of place among cyclists or non cyclists. Been on a couple of rides that "required" cycling apparel. Cycle gear or not, when it is hot, humid or engine get heated up, cycle gear helps keep hardware cooler and reduces risk of chaffing. But you don't need a plastic bag, a good choice is the J&G touring short- look a lot like running shorts, have a thin pad for moisture control and aren't hugely expensive.