All my bikes endure the same amount of abuse...
err...
well maybe the Miyata and Dahon will get winter duty as well since they can run the studded tyres.
Just get a kryptonite NYFU lock and lock it up with that. I use that with my attractive (to thieves) Rossin on small excursions like yours. I try not to keep it out of sight for too long though. Important part is that you immobilize the rear wheel with lock through rear triangle + rear wheel.
just ride it through rain once or twice, you won't worry about scratches or dirt as much afterwards.