With more than a quarter of a century of visiting Deep Creek hot springs I usually tell friends every day is a good day to go there. If it is snowing, raining, clouded or crowded it is still a good day to go. To quote Bill Clinton " It depends on what the meaning of is is."
The best way to go is when you do not have to be somewhere else and have to leave the springs. When I go there I remove anything that tells me the time of day. That works for me because while at the springs I like to be on Deep Creek time. Deep Creek time has nothing to do with cities, schedules or timing devices.
Go and expect the unexpected. But bring plenty of ice, water, time, and a positive attitude. I was a Boy scout once, before I discovered girls. ' Be prepaired ' is a good moto to keep in mind. If you burn easily bring plenty of lotion/sunscreen. If you are really fortunate bring a pretty women to help in its application.
If like the wicked witch of the west you melt when water gets on you, stay at home on your couch. If you do not like crowds go during the week days, but there are crowds during the week sometimes :~) Remember, there are millions of acres to explore if you do not like the crowd at the springs for any reason. This IS the San Bernardino National Forest. Your Forest and your land and your national heritage. PLEASE help keep it clean and pristine, PLEASE !
And that is the best time and way I know of to go to Deep Creek hot springs.
ENJOY !