I lock my bike with both a strong U-lock and a thick cable lock. Never had it stolen, even when I spent a summer in Baltimore. (Though I would take the bike in

I lock my bike with both a strong U-lock and a thick cable lock. Never had it stolen, even when I spent a summer in Baltimore. (Though I would take the bike in at night.) You don't need to have impenetrable security, just better security than the bike next to yours.