I just got back from a partial weekend in Idyllwild, right next to Mount San Jacinto State Park.
I only spent a little over 24 hours there, and wasn’t able to do much hiking due to heavy cloud cover and icing, but man is that place beautiful!
I spoke to a few local hikers I met while walking around the town, and they said the best time to start hiking is usually late May / early June, because you’ll miss the first wave of thru-hikers on the PCT, and most of the ice and snow are gone by then.
According to the locals, there’s about 2 feet of solid refrozen snow on the mountain’s upper reaches right now, so if you are planning on hiking up there — don’t go without proper ice equipment. As for me, I’ll definitely be back this summer.