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.
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.