Sorry about the mix-up in highway numbers. I should have looked at a map for confirmation. I've only lived here 29 years
and watched Blue Diamond Road go from a sleepy 2 lane roadway to a major highway near I-15. Most of us just refer to the many state roads left over from when it was a sleepy one-horse town by the street names. Even those sometime change names over the years. I was nearly in an accident victim (car not bike) on Blue Diamond Rd recently and the state troopers responded to it. Hot as it is right now I only ride as early as possible and plan my routes with lots of water stops. That means I don't ride on the western part of Blue Diamond road where things are far apart. Saw a guy trying to fix a tire around 10 am Sunday as I came down from the mountains. It was awfully hot but I had kids I had to deliver to parents after a weekend stargazing so I couldn't stop. It was getting hot enough to be downright unpleasant.
I don't know what the nearest street is at that point. The road becomes 4 lanes and then 2 lanes just at the point you turn right to go to the park. Look for the gas station on the left. It will be the last building you see on BDR below the mountains. Look for cars parked on the right side well off the roadway. There are enough people who do this ride that you will have no trouble seeing it. In any case, there is enough room to park off the pavement all along that section of BDR. It is mostly uninhabited desert.