Apparently the only time you should be calling a bus-hike group organiser is if there's a problem/question, or if the outing is marked as a pre-registration type in the book. They apparently have more than enough people to fill a bus for all of the bus trips, so they really don't want to hear from every single person "just letting them know" that they're planning to come along. Oops.
However, did learn something useful in calling, apparently the "be 30 minutes early" advice on the activities page is followed so universally that, to actually have a chance of getting on the bus you have to show up 45 minutes early (or more).
I'm thinking car hikes sound better and better... but if we're doing car hikes we can almost skip the scheduled hikes and just go wherever we want (with the appropriate maps). Of course, then we don't have the people available to do car-shuttling, so we'd have to do out-and-back hikes, but those aren't horrible by any stretch of the imagination.