To figure out what is best, you might want to look for results from studies about the effects of returning to athletic activity after concussion. For example, a cursory Google search found this: http://well.blogs.nytimes.com/2008/05/16/sports-activity-after-a-concussion-slows-recovery/. (The basic idea of that study: More athletic activity = slower recovery; the more time off to heal, the better.)
That fits with everything I experienced when I had a head injury. From my personal experience and the medical stuff I've heard:
1. Let yourself rest, or make yourself rest if resting doesn't come naturally to you. If your body is telling you, "Hey, I'd really like to sleep for about 17 hours straight today," you should probably just listen to it and not feel guilty about it. That doesn't mean you can't do any athletic activity (assuming your doctor says it's okay), but I really wouldn't push it with anything that makes you feel bad.
2. Based on what doctors told me, you REALLY cannot afford to hit your head again while you still have any symptoms of your concussion (and I imagine you probably shouldn't do anything that has it bouncing around a lot either). So if you decide you want to ride, I would just be reallllly careful and do not risk falling and hitting your head. They told me that once all the symptoms were gone, I could do whatever I wanted, but brainz really don't like being re-injured while you're still having symptoms of the original injury.
ETA: For people in general who might experience head injuries in the future (as is always a possibility as a cyclist): I know going to the ER sucks, but you can't always tell how bad your head injury is based on how you feel, so it's really a good idea to get checked out. Brains are pretty important. Even if you don't think you feel all that bad, and even if you hit your head while wearing a helmet, it's still possible to have issues like intracranial bleeding, etc. that need to be identified and addressed. Sucks, but it's better to check it out early than to end up having a stroke or other complications later! (Not meant to be directed specifically at you, steve. I just know I didn't fully realize this kind of thing until I had a head injury of my own, so I figured I'd share.)