I don't know if I'd go the bmx route. First of all, way too much work trying to incite a bunch of bikers. Most of them won't care. I'd stick to what you and Dawnie were doing by contacting the city council, land use board, parks and recreation dept., etc..
I think that if the park is on city land, the city might take issue with a skate park that discriminates against certain skaters. Contact the city's legal dept.. I'm sure that more could be done through legal channels than through trying to get the bikers up in arms.
And if all else fails, check and see if people park illegally to skate there. Call in street violations. Check their distance to fire hydrants. Do they smoke on city land? Smoking is illegal, here in Austin, on city property (not sure about parks). Are there any health violations, etc..??
Good luck, Jay.