I'm from the Bay Area and I'm attending CU Boulder, gonna be a junior next year, so I was in the same boat as you. You'll figure out stuff to do pretty quickly, but my advice to you is to just get a car. I didn't have a car my freshman year, and even though I was able to find people to get to the mountains with, it was still a pain in the butt. And IMO, public transit is not that great around (maybe living in Golden makes this different that living in Boulder). If you have your own car you have the freedom to go wherever, whenever, though paying for gas is a bitch, it gets you to the mountains. Find friends to split gas with, and it's really not bad at all.