My favorite in the past was Hot Creek. There were restrooms, a changing area, etc. But the Inyo National Forest has declared it to be unsafe and has fenced the area off and prohibits people from using the spot. The reason given was that the hot spring that came out of the creek couldn't be guaranteed not to scald someone.
I know there are other hot springs in the area, some are commercial, but have not tried them. I hope others can give you come recommendations.
