All of the respondents have suggested that you are being far too optimistic about how fast you can cover distances. If you manage to drive between Nashville and Dallas and actually make it in less than 11.5 hours, I would be stunned. If you have a police escort and could control the driving delays, you might be able to cover this stretch in 10 hours, but I doubt it.At about 575 miles, a reasonable day.Austin to El Paso - I figured since we have the long resting days we will be up for it.
If you are going to roadtrip, it helps if you are willing to embrace risk. Non-risk trips can be had at any amusement park...(i am still very concerned about where to stay here, the whole border town thing kind of irks me).Tucson to San Diego is 410 miles, and even with a police escort you would need a full 6.5 hours to cover this distance, a reasonable driving period would be a tad over seven hours.Somewhere in Arizona to San Diego - I figured we would take it easy with a 5 hour drive to finish it off. Not too bad.
Mark