Californian hot springs can also get overrun, as supply is much less than demand. That's particularly true of places anywhere near San Francisco. For that reason, the prices can also get really high.
There are way too many places to discuss here. If you want to get serious, buy
These springs, inland from Big Sur in the Ventana wilderness, are at the end of about 6 miles of hiking that is pretty painful in parts. The good thing is that acts as a powerful filter of people - not everyone is quite willing to do the hike, and the springs attract a fitter crowd. The springs themselves aren't world class, though I love the one up the cliff that is basically built into a tree. A great weekend trip.
On my hike back from Sykes Springs we were unable to drag ourselves out of the springs, started back late, and became lost in a redwood grove (flashlight broken). That was a bit scary, especially when our lighter exploded and started a small forest fire. However, camped on the path and survived to tell the story.
[Near Sykes Springs]
Wilbur is pretty flawless. It has one of those nice late 19th century Inns that are common to California resorts. Its baths done up in that kind of quasi-Japanese style favored by asiaphiles everywhere, and they look good.
What's worth writing home about is the water. Its a funny kind of green, and it is powerful and very hot. There are even more powerful baths in California (some too powerful) but within striking distance of San Francisco this is a good bet.
Wilbur has a well-equipped communal kitchen.
[Outside of pools]
Orr has a relaxed feel, good springs, and great proximity to redwoods. However, as some report, it also can be a little heavy on the attitude - it doesn't necessarily have the feeling of radical inclusion. It is possible to feel a little unwelcome, and you can meet some major grumps here.
One great thing about Orr is the chance to visit the nearby Montgomery Grove, a little-known redwood grove that has some of the tallest trees in the world. For a while it had the tallest known tree in the world, but someone found a higher one.