The Stanford College Republicans are small, often poorly organized, and not a huge presence. The Stanford Conservative Society has similar issues. Both are somewhat active despite their size, though they don't have the resources to do much. The Stanford Review is the most prominent conservative student group on campus. Sometimes it has good points, frequently it receives a lot of hate, for example, for publishing an article saying people shouldn't vote, another one advocating for a whiter curriculum, etc. Most of the hate it receives is for publishing culturally conservative articles. They don't even veer into social conservatism much. The Review is also highly dependent on its editor. This past year's editor was quite the character, and I believe next year's is a bit more toned down.

Social conservatism has little to no presence on campus. There is a student group that's pro-life and occasionally hold rallies, but nobody really pays attention to them. I imagine Trump supporters will show themselves in the fall, in what will be a very brave move, as they'll receive loads of hate from... well pretty much anyone who speaks publicly about these issues.

Bottom line: there are conservative student organizations you can get involved with. There are conservative organizations elsewhere on campus (Hoover, namely). If you want to engage on fiscal or cultural conservatism, you can find other people to talk to. Social conservatism, well, not so much.