Cal fan here. There's not a lot of easy parking to facilitate tailgating for Cal games. Couple of suggestions:
Faculty Glade/Faculty Club - Great indoor/outdoor area that often sees visiting fan bases utilize before games - https://www.berkeley.edu/map?facultyglade
Faculty Club serves food and alcohol
Cal has a fan fest on our practice field (Maxwell Field) just outside the stadium (northside) with music, food and drink - family friendly
Plenty of good watering holes in Berkeley - Try Henry's, Raleigh's, Kip's, Jupiter, etc - https://www.tripadvisor.com/Restaurant_Review-g32066-d469269-Reviews-Henry_s_Restaurant_Bar-Berkeley_California.html
They now serve Beer at the Stadium and if your seats are in one of the clubs, you can get hard alcohol a well.
Hope you enjoy the game, Cal and the beautiful setting of Memorial Stadium