Yes, but they don't include firearms references. A while back, Oregon DMV put up "No firearms" signs, which made the news for several days. The articles plainly said the signs had no legal backing.
Oregon Universities declare themselves 'gun free', but they can only enforce it by student expulsion or firing staff. A visitor can carry at a university, with no legal consequences.
The DMV is a government entity. It has different rules about prohibiting people form public property than private owners do. Just because the trespass laws do not specifically mention guns does not mean that private property owners cannot ban people from carrying guns on their property.
They only have to ask you to leave. If you do not, they can enforce trespass against you.