In 2007, I moved from LA to Hayes Valley, and I think it was a perfect SF newbie neighborhood. It's centrally located, easy to get downtown (21 bus), a 12 minute walk to Market Street/Bart. Waking distance to other great neighborhoods like the MIssion, Lower Haight, NOPA, Fillmore, and Japantown.
There's tons to do on Hayes Street which is full of boutique shopping, restaurants, cafes, coffee shops and a few bars. It's lively, fun, and friendly. I loved having stuff to do just outside my door. There's a sweet little park on Octavia where people bring their dogs, kids, and picnics. Recently the city has installed some popup trucks/trailers with ice cream, a butcher, and Ritual Coffee. If the arts are your thing, then you can walk to the Symphony, Opera, theatres, and Asian Art museum.
Hayes Valley does have it's share of section 8 housing, so caution should be taken when parking and walking at night. That being said, I lived literally across from one complex for 4 years and never had a problem.
All in all, I would highly recommend Hayes as a place to live for San Franciscans new and old.