While I cannot find an regulations or laws that directly mention the DMV with regard to your inquiry, I have found the following:

California election code section 319.5 "319.5. "Electioneering" means the visible display or audible dissemination of information that advocates for or against any candidate or measure on the ballot within 100 feet of a polling place, an elections official's office, or a satellite location under Section 3018. Prohibited electioneering information includes, but is not limited to, any of the following: (a) A display of a candidate's name, likeness, or logo. (b) A display of a ballot measure's number, title, subject, or logo. (c) Buttons, hats, pencils, pens, shirts, signs, or stickers containing electioneering information. (d) Dissemination of audible electioneering information.

A note on free speech (similar to what you drew upon above): "We all have freedom of speech, even corporations, but commercial speech is generally regulated differently than political speech, especially on public property. While some cities allow any speech in public areas, others may require you to get a permit before handing out advertisements for your business in public spaces." Taken from here.

And depending on what municipality that you are in, there are different statues that regulate handbill distribution. I only included California because I realized that you had linked to the ACLU California website - and I figured that you were in California.

So while it is not clear that all California DMV locations will be polling places, they are state run (or municipal) properties. Which for all intents and purposes makes them private properties that are able to determine what activities are able to take place on their premises. Public places (i.e. parks or sidewalks) in many cases require a permit for handbill distribution. Other portions of California state law suggest that the permission of the staff at the government agency or office (the DMV in this case) needs to give you permission before you can distribute anything on their property.

Non public forums (as you mentioned in your second comment) include places like the DMV.

I suggest taking your research beyond just the ACLU and looking at California's state laws, California election law, and municipal statues -- but only if I haven't convinced you yet that this is not a very good idea and you should find another location.

End rant.

But note*, I want the same thing you do, I want Bernie to be elected. But there are better ways to go about getting the word out than canvassing or distributing hand bills at the DMV.