hi,
Great place to visit. As Vanilla has said it is a 3 or 4 hour drive from San Francisco. We hired a car and it was an easy drive.
It is quite expensive to stay in the Park, as they use the revenue for the upkeep of the park.
You have a choice of a canvas cabin, which is like a military tent, with a wooden floor, and a metal framed tent about 6 foot high with a bed inside.
a big step up from camping, but not heated, so bring your tracksuit and woolly socks to sleep in. You can also stay in a heated wooden cabin which is more expensive. There are hotels which look nice, but pricey.