The cool part of town where the new billionaires live is The Mission. Note that it is a transitional area with a more crimey side (east) and a more gentrified side (west). This is also the area where anti-tech-worker sentiment, violence, etc. is most common. The Castro is a nice, vibrant gayborhood in the south. The Tenderloin/Civic Center/Western SOMA are pretty gritty, but other than that the entire northeast quadrant is nice and walkable. The western half of the city has a more suburban flavor and worse weather, but it's cheaper.
In general, I'd recommend you take a short-term rental to explore the city rather than trying to lockdown a long-term rental from afar. Especially because the open houses are often open for an hour or two and result in waiting lists (dozens of would-be tenants) in length.
Also, just be aware of rent control. I think the market prices aren't any different between older (rent-controlled) and newer buildings, but after a couple of years of 20% pa price increases for the non-rent-controlled place, the rent controlled unit will be much relatively cheaper.