I spent some time in Lake Tahoe this summer, mostly South Lake Tahoe, and there were so many cyclists. It was such a joy (admittedly I was on vacation) There were many designated multi use paths for walking/cycling/scooters, in addition to bike lanes on the street. It felt safe enough that I could park my bike in front of any restaurant and eat without worry that someone would steal my bike, which was a big plus. There were even some touristy spots where they would encourage people to park there bikes without locks, which was surreal for me. It seemed like many people that live there own 4 wheel drive, large vehicles, but also own bicycles and made use of them during the warmer parts of the year. It felt like they figured out how to make cycling and other forms of transportation work well for their city.
In San Francisco, I can commute with my bicycle year round, except for heavy rain, which then I can easily take a train or bus (or drive but why bother). San Francisco has green painted lanes on the street, designated bike lanes, and areas for bike friendly rides, like the Embarcadero's multi use path, car free Market St, Golden Gate Park, etc. I still don't feel comfortable street parking my bike in most parts of the city unless I'm being quick. I do use BikeLink Parking whenever possible since it's the best and offers me peace of mind. I find myself biking to areas with BikeLink parking available instead of somewhere closer without it. I know some cafes that allow me to bring my bike on to the patio, so I can make it work for many things.
Which city has a stronger bike culture? and bike infrastructure? I think SF would benefit from more multi use paths like they have in South Lake Tahoe, but are they mostly a benefit mostly for tourists and not commuting? I wish SF had safer bicycle parking, since it is such a wonderful way to commute around the city. South Lake Tahoe was a little hot, and SF always has the best weather, so it's easier to ride in the sunshine.
Dunno about bike infrastructure in San Francisco as I've only been there a few times, but one variable you should mind is that South Lake Tahoe is snowy during a good chunk of the winter. Don't plan to move there and bike around unless you're comfortable biking in the snow.
It can be warm in Tahoe in the summer, but the snow is a certainty and cannot be avoided if you're living there. Tahoe is usually fairly mild, or it has been while I've been there. It's also way high up in elevation, which can cause respiratory problems for some until they acclimate.
Even though it snows during Tahoe's winters, it was wonderful to see they have still invested heavily into bike infrastructure. It seems like they have figured it out for their cities, creating space for cars and bikes/scooters/walking/etc. I don't fault people for owning cars who live in cabins in the deep woods, so it was surprising to see the amount of people using bikes and scooters, even locals for commuting and doing errands.
I did see cans of air for sale in Tahoe which make me smile. I'm so glad I brought my bike on vacation because it seemed like everybody else did as well.