best route from south lake tahoe to sacramento

Take the 50. The only challenge is the climb out of South Tahoe, not a big deal.

Probably way late for this, but I have an interesting story about US 50 vs I-80 into Sacto from the Lake. In 1976, my new bride and I rented a 22' U-Haul truck to move to Sacramento, from here outside of Philly. I was finishing school at CSU there. We took I-80 most of the way west, rumbling along at 55 all day long. We stopped at Tahoe for the night on our last day. For some reason, I was under the impression that I-80 was a real "horror" for trucks with all the curves and grades and such, so I somewhat foolishly decided to use US 50 instead. The next morning we navigated around the lake, and then headed down 50. At the time, at least to a young 23 year old not used to mountain roads, in a big truck, it was far more of a white knuckle drive than 80 would have been, but I still remember as clear as day the swooping curves coming down past Placerville and the other towns up there in the foothills, and seeing the golden California fields stretching off into the distance. It seemed like we were driving in a magical land. We finally made the flats, and as luck would have it, US 50 went right by the married student housing complex we were scheduled to live in, right off Howe Avenue near the CSUS campus. If we'd taken I-80, we'd have been way north of town, of course, and would probably have gotten lost finding the college :)

South Lake Tahoe to downtown Sacramento on 50: 101 miles.
South Lake Tahoe to Sac going around 89 to Truckee and then 80: 142 miles.

50 is a much easier road than 89 around the lake so the only possible reason to take any route other than 50 is if 50 is closed, or you need to go to Truckee.

But since your final destination is San Francisco, depending on time of day and day of week, you may avoid a lot of traffic by taking 89 out of South Lake over to 88 and then 88 all the way into Stockton and cutting over to SF from there. It's actually a longer route, but 88 usually doesn't have a lot of traffic, while 50 could be jam packed depening on time of day.

We came down 89 and took 50 into Sacramento with a slighter bigger fifthwheeler. You should have no problems.

Two Hands wrote:
You could go north to Truckee then west on Interstate 80. It will be a bit further, but doable. We driven both routes without any problems.

Did you take Hwy 89 around Emerald Bay? I felt a bit queezy with just my truck. :)

You could go north to Truckee then west on Interstate 80. It will be a bit further, but doable. We driven both routes without any problems.

That is the only good route.

Yes.