Favorite university to visit for away games ? Transfer at MacArthur station to catch the train going towards Pittsburg / Bay Point. Take the 6 from Orinda or Lafayette:
https://countyconnection.com/routes/6/
At night when school is in session (not summer), you can also take the 250 from Bart as well.
https://countyconnection.com/routes/250/
If I had known about the Gael shuttle 250, I probably would have gone to more Gael basketball games as I lived in the Oakland Hills and could have taken the bus late. Like you, I take mostly transit for games. If you are looking at the Dec 9th Wms BB game at SMC, it is a 1pm game, so you should be able to do a day trip via BART and Capital Corridor no sweat.
EDIT: Also, walking, sure, but SMC is much more compact than Cal or Davis. There are some small hills, but nothing too difficult so not much walking at all to McKeon Pavilion from the main entrance. I've done it before its about 5-10 mins at most. My HS had academic and athletic events there and it also hosts west coast college fairs at the college so I'm pretty familiar with it.