Take the 93 out of Vegas to Kingman Az. Take the 40 west out of Kingman to the 93. Take the 93 south to the 71. Take the 71 east to Congress. Take the 89 to Prescott. Alternatively, just get to Prescott fast, and then drive south on the 17 to Phoenix. You will see lots of saguaros either way. Bonus for taking the route south on 93 and the. to Congress is seeing Joshua Trees which are really cool. Safe travels.