I haven't heard anything about any Gopher meetups in Denver, but I also am hosting my parents 50th anniversary on Friday at our house in Golden that night, so haven't been looking.
As far as getting to Boulder, you have a couple options. You can check the RTD schedule -
https://www.rtd-denver.com/app/route/FF1/schedule?day=saturday&direction=westbound - and take a nice bus from Union Station in Downtown Denver to the Baseline & Broadway stop in Boulder. That will drop you at the south edge of campus and the walk to the stadium is probably 10 minutes through campus to Folsom Field. You will walk past some tailgating parties on the way as well. You could also take that bus back down to Denver in the evening -
https://www.rtd-denver.com/app/route/FF1/schedule?day=saturday&direction=eastbound - Last bus leaves from Downtown Boulder (where Pearl Street and most of the bars and restaurants are) at 11:30pm or Broadway and Baseline at 11:36pm.
If you're not worried about money as much, I'd just take a Lyft or Uber from Denver up to the game. You'll probably spend anywhere from $30-$50 each way depending on how busy it is. Beware though, the later you stay in Boulder it might be harder to get a ride back down to Denver. Meaning if you stay til 11:30 or later, it sometimes is harder to get Lyfts/Ubers in Boulder.