The maypole tradition actually starts the night before in most villages, when local men gather and enjoy beer while guarding their maypole against theft from neighbouring villages. So the way to defend a village's honour is to set up tables over the maypole and sit there all night drinking beer. If another village is successful in stealing the maypole before it is erected on May 1, the ransom is also usually beer. It is a highly local thing, though, so just joining in might be suspicious in very small villages. But I am sure a Bavarian tourism website would have locations of where you can join in. If you can find a place that puts it up by manpower, it's probably worth seeing.
Not sure who decided this was the way to go, but it is genius--way better than wars and such--in terms of "defending the town's honour."
As for your question about festivals, yes, you can just go. They are meant to be enjoyed by everyone! They would have rides, carnival games, and beer tents--very similar to Oktoberfest, actually. With fewer tourists and slightly smaller crowds.
If you prefer, travel north to the Harz for Walpurgisnacht and join the witch festivals. May 1 is a holiday and falls on a Monday this year, so no matter where you go, expect crowds and great atmosphere.