Presidential rallies could be a great venue to show off your cargobike. On this occassion, I didn't bring a cargobike and decided to walk instead. I was glad to see these local cargobikers share the cargobike love to thousands of people.
Here are a few ideas: Attach a slogan placard, US Flag; sell some refreshments; shuttle people to the nearby restrooms or coffee shop. There were entreprenuers selling t-shirts, buttons, hats, and more but none of them use a cargobike. So offer to carry their merchandise.
In San Diego, we were fortunate that the weather was very favorable as we waited in line for several hours to get in the convention center. We walked from Balboa Park for 30 minutes to get to the marina. The return walk took fifteen minutes longer as we lingered at the Gaslamp quarters.