I've got one of these handy dandy Cingular deals with GPXSonar on it. If I don't have a current page in GPXSonar, just click the waypoint and BANG I'm connected to the realtime cache page. I have been in out of service areas that screw this up, but I've got the thing strapped to me anyways, might as well use it. I've even occasionally done the nearby caches search and gone after one I hadn't previously bookmarked.
But sometimes I print the cache page and hit the road, manually entering the waypoint as I drive. LOOK OUT!