Ellis St, San Francisco is this area safe for 2 25yo girls travelling by public transport

Public transport is very safe here. I've ridden subways and some buses in at least a dozen cities in the US and abroad and I feel safer here than anywhere. Obviously, you should be aware of and control your belongings, but I don't think it requires any more than a normal level of vigilance. As far as personal safety, 2 25yo together is totally safe, as long as you both are sensible people generally, and neither of you are pass-out drunk. Even late at night, I would say it's fine. I often ride alone late at night and rarely have even the slightest concern.