I wear lycra shorts under my $20 shorts or my swrve jeans. I have a bunch of castelli stuff for my centuries out in farmland. The constant is road shoes. If I need to go mobile then the backpack with lock and flip flops.
But in all honesty, it cannot be said enough, it's has to be cold for jeans. I don't ride around at 7-10mph, and I sweat accordingly.