I was at Jetty Park in March (for Nationals Spring Training) and took in a night-time rocket launch from the beach, which you can easily walk to from the campground - just go out the gate. Wasn't very crowded, although from the beach the rocket is mostly a rising ball of flame, but you hear the roar of the engines, too. Might be more difficult to watch from the close-in viewing locations at the Space Center, but I think they charge for that space. Didn't notice any road closures or signs re-directing traffic.
