I've been commuting to work via motorcycle for six or seven years now, though I'm in Seattle not the Bay Area. Here is my generic advice:<p>Don't buy a shiny new bike to start on. You WILL lay it down and scratch the paint up - everyone does. But you'll stand it back up again and keep riding, because laying a bike down is not that big a deal.<p>No matter what you're intending to end up on, start with some fairly inexpensive ten-or-more-year-old Japanese bike, preferably a Honda. You want something simple and reliable, not something you have to tinker with, and a machine whose maintenance is cheap and easy, because it's all going to be unfamiliar.<p>The standard wisdom is that a beginner should start out on a small bike, 250cc or so. This is because small bikes are lighter, which makes them easier to handle, and because newbies often get in trouble by yanking on the throttle when something startles them, so you want to have less engine going crazy when you do that.<p>If you're going to be riding I-280 every day, though, I think you'll find that the low power of a 250cc bike will make life a little bit scary. Part of what keeps you safe on a motorcycle is the fact that you are faster and nimbler than everyone else around you. Cars rely on metal frames and bumpers and airbags for safety, but motorcycles rely on getting the hell out of the way. You'll probably want a 500cc-600cc bike to start with, so you have the option of flying away at 80 mph when you need to.<p>My current bike is a Honda Nighthawk 750 and I think it is probably the best commuter bike ever made. It is not exciting, but it is sturdy, reliable, and handles freeways with no problem. (Top speed is roughly 100 mph.) I've taken it on long weekend trips, too, and while it's not the most comfortable cruiser ever, it is certainly up to the job. But mostly I just go back and forth to work, and it just keeps on ticking, and life is pretty darn good. I'm not sure how it would work as a starter bike - it's a little on the heavy side - but if you're a tall guy it might work.<p>I get about 40 mpg. It is possible to do better, but I am a relatively aggressive rider.