Disclaimer: I'm not familiar with Lompoc. That looks like class echo airspace in which a radio is not required. Apparently the airport's control tower only operates part time. Still, with nearby population centers, restricted air over military bases, possible gliders and skydivers in the area, even oil wells relatively close, it looks like a particularly foolish place to turn an aircraft into an unguided missile by jumping out of it.
Ok I'm surprised. I don't think anyone here in Europe flies without a radio. If only just to monitor local traffic. Most of the flying club members even carried backup portables. I didn't proceed to my full license so I never did. But I did have lots of ham radios on which I could receive (not transmit) the airband if needed.