I spent a summer working out of an office in Menlo Park. Having just come from Manhattan, it blew my mind that you had to get in a car to just get lunch. How do people live like that?
Cars zoom by, there were two sets of lights which took nearly 15 minutes of waiting to navigate and on top of that drivers look at you as if you're some sort of pariah (felt like it at least!).
Very, very different to what I'm used to in London and sad to be honest. The valley is an incredibly beautiful part of the world and it seems urban planners decided to cover it with miles of single story buildings and car parks.
In America you're probably a bum, have a drunk driving conviction, or are otherwise outcast or not where you should be. If you are waiting (and waiting...) near a bus stop early enough in the day you might be taken for an honest but low-wage worker. But if you are on a dilapidated bike in some parts of town it's a sure bet you are on your way to a mandated alcoholism recovery program.
On the other hand if you're on a $3000 racing bike along the edge of the Bay then chances are you're an "honest" tech-worker commuting down to your job at Google from your swanky apartment in San Francisco's Mission district.
The problem is that the strip malls are designed for access by car. That means being close to multi-laned expressways, at least in most of the suburbs. San Jose proper actually has a decent (for the US) public transit system, including Caltrain, the VTA light rail, and a bunch of buses. They're optimized for commuter service, though, and will only take you few interesting places.
The downtown area of San Jose, though, is pretty walkable and isn't too dull (sure, it's no San Francisco or London, but what is?) San Pedro Square has some nice restaurants, and you can head from there to the park and then up Paseo de San Antonio to the university and cute coffeeshops. If you're up for more of a trek (or a few more stops on the light rail) there's a decent little Japantown a little ways to the north as well.
1) Social inertia: you're going to be the only one doing it, and feel like a pariah. It also feels like you're holding everyone up because they basically expect to be able to turn across a lane that now has a pedestrian.
2) Poor design: you have to take a bizarrely circuitous route that makes you ask, "okay, did anyone actually try using this before final approval?"
Especially sharp contrast going from my office in SF to the Googleplex in Mountain View -- in the former, I could stroll around, take a walk, go wherever. At the Googleplex, you end up having to take unofficial routes between buildings -- walk up a sharp driveway (shared with cars) rather than the out-of-way sidewalk, dart across a busy street while traffic is held up, sometimes waiting on the median for the other side to clear up. Yuck.
[0] Example A: Lived in apartment catty-corner from my (large) university in a small town. Much of the route didn't have a sidewalk, just a curb and some dirt/grass. People would actually ask if you needed a lift! No, just walking to my apartment, 1/3 mile away!
Example B: Lived in an apartment directly across the street (a two-lane, slow one) from a shopping center and less than a half mile from a bar -- but again, drivers don't expect you to cross the street or walk alongside it, and no sidewalk to the bar.
(Just realized this post has a ton of words that are different in British English.)
At least in SV the weather is nice and the roads are good and the landscaping in the parking lots is pretty. The office park suburbs of northeastern cities are a desolate and disgusting place.