You make it sound like you're going to church. Just go w/Mom in normal clothes. (Your Mom can use this as a barometer If these are people she wants to deal with) If they judge you by what you "appear" then screw them. I work with TONS of folks - long hair, blue jeans, tats - if sales"person" shuns them he finds another. If the others do too, (one guy I worked with/for) walked into GMs office and told him that he had $90k cash burning holes in his pockets and sales people don't seem to want to sell him a car. (This was at a Benz Dealer) Then proceeded to tell entire new car sales dept to go fuck themselves. They just assumed he was some "punk". I wouldn't call Ed Roland a punk (those who don't know - of Collective Soul)
Bottomline, do your test drive in what you normally wear to drive in, if the dealer has a problem with that, you don't need to shop there.