It is $10 to use the basic hot pools and steam room, $30 per person to have access to everywhere and extra if you want to get a massage or another treatment.
You could also take a bus here: lines 11, 12, 27 take you very close. But i would have to recommend taking a taxi home because after hours in the hot pools you have no strength in your legs.
Another tip I heard was that they change the water of the pools on Thursdays, so it is cleaner to go after Thursday. There are other hot pools in the area but this place is nicer than most. And apparently they are open all year round too.