Fridge Brilliance: The guys seemingly violate San Dimas Time at the end of Bogus Journey, but it can be explained if they switched places with themselves from 16 months in the future.
Of course Future!San Dimas is a utopia - this is a future in which God, heaven and a personification of Death himself are conclusively proven to exist, not to mention time travel (which was probably given to humanity by De Nomolos or Rufus in a Stable Time Loop). This probably goes some way to explaining just how Wyld Stallyns are so massively successful.
The first film begins with Rufus explaining how utopian the future is, but he talks about how "bowling averages are way up, mini-golf scores are way down," and Earth has the best waterslides in the galaxy. It seems merely humorous that he would touch on such trivialities, but perhaps this shows that in Rufus's time, peace and prosperity have been known to the people for so long that they don't even care to mention it if someone asked what makes Earth good. Rufus rattles off hobbies and pastimes because life is just so good that it doesn't even need to be mentioned that there is no more war or environmental concern or other things more pressing to modern people.
Fridge Logic: In Bill & Ted's Bogus Journey, when the Evil Robot Usses reveal the their robotic innards, it causes many people to faint (even the princesses), yet when the robots do this to the real Bill and Ted, the latter don't seem to faint at all. Immunity, perhaps?
By this point, Bill and Ted are probably quite used to weird stuff happening to them. Of course, the princesses are technically time travelers as well, but still not nearly as used to weirdness as their boyfriends.
Why would everyone go home before the last band played at the Battle of the Bands? The 'Battle' isn't over until every band plays, but apparently in San Dimas, people are content to see a few bands play, and then read about who won in the newspaper the next day.
Fridge Logic: In "Excellent Adventure", the duo bring a number of famous people from history into the present. Four of these (Socrates, Billy the Kid, Joan of Arc, and Abraham Lincoln) had deaths that could have been prevented if they had known they would happen. By travelling to the future, they have been given the opportunity to learn about their impending deaths and possibly prevent them. Bill and Ted may have altered the course of history.
It's properly a case of Hitler's Time Travel Exemption Act. If they had learned about their personal futures offscreen, there would have been an offscreen conversation that says they have to go through with it anyway to prevent changes to the future.