Are there self-service vacuum cleaners available here? If so, is there a charge, or can someone just drive up and use them for free?

Yes they have them

We do have self service vacuums that run 24hrs - they are $1 for 4-1/2 minutes - they take only quarters and there is a change machine on the outside wall of the Car Wash - thank you for your interest in this matter

Yes there is. Bring quarters

Yes. They charge 4 quarters for about 5 mins.