You didn't say whether developed or primitive . . .

Mono Hot Springs, east of Fresno at the end of CA168, a mix of developed commercial and free primitive soaking tubs along the headwaters of the San Joaquin River;

Mammoth Lakes area along 395 with a large number of primitive and rustic hot springs (Iva Bell, Red Meadows, Whitmore, Wild Willies, Hilltop, Sheppard, and Hot Creek)

Buckeye and Travertine (both primitive) further north past Mono on 395 near Bridgeport

Walker Hot Springs (primitive) across into the Sierras on the Nevada side; prolly not accesible with the snows this early in the year.

I'm not aware of any within the park itself (except Red Meadows near the Devil's Posthole on the east side of the park). . . those listed, I can post detailed directions for those you're interested in.

Rick