For me the HUGE advantage the CNG vehicle argument has over Electric Cars, Plug-In Hybrids etc, is that the vehicles actually exist TODAY and have been built at competitive prices for a decade or more. Most people have never heard of driving on CNG, don't know it's possible; sp this march on Washington is a golden opportunity to show average Americans that Natural Gas vehicles are a reality and offer just the sensible and practical alternative our ailing economy needs.
First, everyone who drives a new or converted CNG vehicle, including fleet operators, Municipal buses, the new Freightliner tractor trailers, as well as the thousand or so Honda Civic GXs, and at least 1,000 converted cars from Utah and Oklahoma needs to drive these cars to Washington DC. Of course Clean Energy would need to install refueling pumps along Interstates every 200 miles from California, Utah, Oklahoma and New York to make these cross-country trips possible, but what an impact for Americans to see these cross-country trips being made WITHOUT ANY PETROLEUM!
The CNG solution is very concrete, backed up by proven hardware, and based on fact. It shouldn't be approached the same way as an emotional or belief-based political issue like Gay marriage, or Civil Rights. So let's present the FACT OF THE CNG Solution by "Demonstrating It" instead of "Demonstrating FOR It".
P.S. If public parkland is a problem, we could merge the "car show" portion of the March with a CNG vehicle industry trade show and rent out a big convention hall in D.C.