If you have a rugged 4WD with high clearance and you DON'T MIND treating it roughly and getting it dirty (most SoCals treat their SUVs with the delicacy of a newborn, which always puzzled me...SPORT UTILITY, people!), you can access the Deep Creek Hot Springs trail via a network of rough roads across BLM and National Forest land. It will cut off about 1/2 mile of steep hiking, and you won't have to pay the $4 per person fee at the Bowen Ranch.
Follow the same road directions to the Bowen Ranch Road, but turn left on Oak Springs Road instead of staying right to the ranch house. Then take the next major right turn, and another right at the T-junction onto Forest Road 3N59A. Proceed down this rough road for a mile or so until you see a large metal sign at a parking area. You can park here. Overnight camping is officially not permitted, but people occasionally do.
Walk down the road past the parking area, turn left at the metal trail sign, cross the fence, and follow the normal trail directions for the remaining 1.5 miles to the springs.