That depends on whether you get ADSL (6 Mbps per copper phone line, resold AT&T, but a real phone line) or Fiber Optic (gigabit fiber optic to the apartment, but you get an additional box that exposes a phone jack plugged into the ONT in the closet, so presumably VOIP).
ADSL2 goes up to around 20 Mbps, VDSL up to around 50 Mbps. Sonic may or may not still sell bonded DSL service. I believe the only resold AT&T service these days is the FTTN offering (resold U-Verse with all the nastiness that involves).
Where I was living in SOMA, it was resold U-Verse that wasn't even FTTN. It was several thousand feet of copper back to the central office. No one knew the exact length, as those records were lost.
Was ecstatic finally moving away from that place to somewhere else.
I've had ADSL2 and VDSL on Bell Canada lines in Ontario, but last I checked (maybe four years ago?) I was under the impression that in SF proper AT&T wasn't able to get permission to build out the nodes to do FTTN/VDSL in many parts of the city.
Since then, I've only lived in new construction where they have fiber to the unit...
ADSL2 goes up to around 20 Mbps, VDSL up to around 50 Mbps. Sonic may or may not still sell bonded DSL service. I believe the only resold AT&T service these days is the FTTN offering (resold U-Verse with all the nastiness that involves).