It's hard to go wrong on that trip, just take time for side routes. I say blast through the midwest and take as much time as you can in the 4 corners area. Ouray Co down thru moab (take the canyon cutoff) to monument valley mehbe. In Sand Diego you'll be "near" some great places incl palm srpings/joshua tree/Johnson Valley and Giant seqoia on up to pismo.......if youve never been arches, grand canyon, mesa verde, durango...don't dawdle to long on the front range in boulder