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Your general plan will work just fine, but a couple of minor 'tweaks' should make it even better. Since you want to stop in Las Vegas on your way out to Anaheim, the route that works best for that is to take US-78 from Birmingham to Memphis and just follow I-40 west. At just under 2000 miles this leg will make a very comfortable 4 day drive. Since we normally recommend around 550 miles as a good target for a day on the road, you should be able to get to northern Arizona with enough time to take the afternoon of the fourth day on the little 'detour' north from Flagstaff on US-89 to Cameron, then west and south on AZ-64 along the Rim Drive of the Grand Canyon and then still make it across the Hoover Dam and on to Las Vegas by late evening. Depending on how far you've gotten by the end of the third day, that fourth day could be a relatively long one, but then you're going to be 'resting' in Las Vegas for a couple of days afterwards.

On the way back, when you have more time, you can take I-10 to west Texas and then I-20 home. Places worth looking at along this route include (but are certainly not limited to) Saguaro National Park, Kartchner Caverns, White Sands National Monument, the Sixth Floor Museum in Dallas, Gibsland LA (where Bonnie and Clyde got gunned down), Vicksburg and others. Again, this is about four days of driving, so you can spend your two 'extra' days enjoying time spent at those sites or even looking for other nearby sites that appeal to you and your boyfriend.

AZBuck