Most definately weekdays are more clothing optional than the weekends. There are usually less people on weekdays and the clothing optional ratio is generally higher than on the weekends. With the warming weather, on a weekday you should be able to free hike (aka clothes free) from the parking lot all the way to the springs without passing anyone. If you enjoy the "optional" experience you should try the hike in and out sans clothing. Once you have done it you will not want to hike in or out any other way ;-)
I have been to the springs on the weekends and there have been 30 to 50 people and less than a handful of us were clothes free. I hope you can make it out on a weekday to see the difference, much more peaceful and relaxing. Please help us all and keep the springs trash free, try to pack out more than what you bring in. Every little bit helps.