Vicky, I hunted high and low in West Oakland. Knowing your house isn't far from mine, I suspect you have the same issue: Sonic will have the same problem as any DSL, since they all run over the same phone lines, and the distances from the phone switching station can be pretty far out here. I am a very happy Sonic customer (and always like to remind people they are the ONLY business that scored high on the EFF's first "When The Government Comes Knocking Who Has Your Back" campaign. I would *VERY HIGHLY* recommend you call them before making any change, as they will take a look at your traffic patterns, your line distance, etc., and maybe be able to suggest something. (What speeds are you having most issues with -- upload? Download? Everything?)
Webpass is available only if your building has it.
There is *one* option that for some reason does not seem to be advertised in Oakland, but is well worth looking into: Clear, which is a 4g wireless option. Bonus for being able to take your modem with you and sit in the park! I had a house guest one time who had it, and it worked fine here.
If you do go with Comcast, I'd urge you to go with a slow speed (their slowest are pretty dang fast unless you have a house full of gamers or something) and avoid any of their 1- or 2- year contracts! Unless you really plan to finish them out. They're bastards about those.