We are also planning a Southern Tier Tour in 2008. Although I love the Adventure Cycling Association some of the routing puts cyclist on poor road choices from my experience. The Southern Tier is no exception to this. I recently used some of the ACA maps on a tour from Maine to Florida. And again found myself on some horrible roads.
I started a forum under the title Southern Tier Roads to Avoid on this web site.
http://www.crazyguyonabike.com/forum/?o=ltIt is worth looking at. I am in the process of redesigning the route to avoid the high traffic areas and shoulder less roads. I also plan to travel southern AZ instead of Phoenix. I lived in Tucson and know that is a nicer area to cycle.
Ending in Oceanside seem like a better choice also.
My suggestion is a combination of ACA maps and your own routing. ACA maps have plenty of useful information on them even if you dont use that particular map. We are experienced touring cyclist and racers and find a trip like this takes us months to plot. For us we try and avoid the big cities like the plague and prefer to go out of our way to ride on low traffic roads. If we have to go an extra 50 miles to get on a better route that day we do it. This may not work for you if your time and speed have constraints. We normally average about 100 miles per day loaded.