From Los Angeles I-15 north to St. George. Bluff St. off-ramp (south end of town). Turn left. There's a north and south entrance to the park. The north has less traffic congestion and has a nice view as one descends into the canyon.
Snow Canyon is a very easy, uncrowded park to work photographically. One can photograph in the morning, return to St. George for lunch and return later in the evening.
Snow Canyon State Park is a short drive from St. George, Utah. I've always preferred the Petrified Dune area towards the north end of the park. I arrive before sunup, climb to the top of the dunes, and get set up for sunrise. The dune area provides unlimited foreground designs and patterns for deep scenic compositions. A good rain will fill the dune's potholes as shown in this photograph. Summer can be extremely hot. My photo time in the summer is done by 8:30AM. All other seasons are excellent.