El Paso to SD on the ST would be advisable as that is an option for you. No significant weather worries. You can avoid Phx altogether by using the interstates to get around it, but that would be no fun at all.
I've ridden Phoenix a good bit. It ain't great, but by staying off the main highways, as ridable as most large cities. Besides, I think the ACA maps will direct you onto the
Canal Trails that will take you from the east to the west side. That may take you a couple of days.
Only down side, east to west, you'll likely encounter more head winds, tho the fickled spring weather rule will still apply. And the scenery will not be as spectacular as your original route. But, you'll be seeing the desert in full bloom as compensation.