I haven't been to Cupertino in many years, but from what I can see on maps and aerial/satellite images it looks like it hasn't changed a lot since I lived there.
My recollection is that "suburbs" is not really a good description. Suburbs bring to mind mostly residential neighborhoods with a few big shopping centers here and there, and not much within reasonable walking or biking range. Places where you find yourself often saying "I'll pick that up next time I'm in the city".
What it felt like to me was more like if you took several small towns and pushed them all close to each other. I could for the most part get around on my bike, but would occasionally want to go to something too far away (e.g., up to Stanford's bookstore for the annual Springer-Verlag sale).
Because it was like a bunch of small towns pushed together, with a layer of residential neighborhoods between them, there were almost always routes for biking between where I was and where the little pocket of density I wanted to be was that would mostly go through those very low traffic residential neighborhoods, so it felt much more safe and relaxing than biking in a major city.
(Wow. I just checked rent at the place I used to live. It was called the Villa Serra Apartments then, but is now called the Markham Apartments. I was paying $750/month for a 750 sq. foot apartment in 1991. Now they want between $3100 and $3800/month. Inflation alone would make $750 in 1991 about $1400 today. That's about 2.4% per year. To go from $750 to $3500 would be about 6.1% per year. Ouch!)