Two places I know of:
Grand Central Sauna & Hot Tub
Address: 376 Saratoga Ave, San Jose, CA 95129
Hours: Open today · 10AM–1AM
Phone: (408) 247-8827
It's near the corner of Stevens Creek Blvd, set back from Saratoga Ave. behind a (former?) card club.
IIRC it's $20 per hour per person and opens 10 AM to late night - double check for updated information - I'm going off old memory.
It's borderline sleazy, doesn't quite feel filthy - I've had good times there 2-3 times.
(My impression is that the clientele is 1/3 providers/clients, 1/3 gay guys, 1/3 "legit" hetero couples.)

The next place, Watercourse Way in Palo Alto, has an upscale reputation, not sure how much of their business might be providers/clients nor how well such couples might be welcomed or discouraged.  Check the link.

200 San Pedro Rd, Daly City, CA 94014

Tuesday 11AM–11PM
Wednesday 11AM–11PM
Thursday 11AM–11PM
Friday 11AM–1AM
Saturday 11AM–1AM
Sunday 11AM–11PM
Monday
11AM–11PM

-- Modified on 2/14/2017 1:39:41 AM