You could also take I-15 south to either 17 (a short cut) or Hwy 9 (both around St. George), and head east into the park on Hwy 9 toward Hurricane and Springdale.
You'll avoid going through the tunnels as you would coming from Mt. Carmel Junction.
Full-Timed for 16 Years
.... Back in S&B Again
Traveled 8 yr in a 40' 2004 Newmar Dutch Star Motorhome
& 8 yr in a 33' Travel Supreme 5th Wheel