I agree, wear whatever you like, whatever your age. Dress codes are bad enough when you have to stick to them at work, so might as well have some fun on the bike. I like cool jerseys, hate most of the girlie frilly ones I have to admit, but fortunately, being 6 foot, a small men's tends to fit me perfectly. Really like the fosca ones, this one is next on my shopping list (AND it matches my water bottles!!! ):

http://www.foska.com/acatalog/Pirate_Road.html