Hi there, we have had the FTTN single speed through ATT with Sonic for a few years and are quite happy with it. Speed depends on distance to the note. Here in San Jose we get
25ms ping, 23.5 Mbps up and 1.8 Mbps down
with speedtest.net .
The service is generally very reliable, every once in a while the ATT Uverse gateway RG5268AC modem needs to be reset (unplug,, wait 10 seconds, plug back in, wait a minute to reboot) but other than that no issues.
Hope your install went well and you get decent speed and ping in San Carlos.