Southern Tier Advice

Hi Folks,
My wife and I are scheduled to arrive in LA from Australia mid Feb 2004 with the view to complete a self contained cycle tour across to Florida and back with the assistance of Amtrak.
We have made plans previously to tour the northern areas of the US during summer several times during the last few years but have never made it - seems other events make it difficult to get there at that time of year, hence why we have settled on riding the south - time of year and weather suitable - at least we hope.
The purpose of this post is to get feedback from others who know this area and can toss us a few tips - like which sections are a "must ride".
At this stage we are limited to a month, hence the reason we intend getting an Amtrak pass - ride a couple of days, train a day etc.
The Adventure Cycling Association's "Southern Tier" cycle route ( San Diego, Phoenix, El Paso, Sanderson, Austin, Mobile, Jacksonville) appears to run reasonably close to the Amtrak route.
We have done a fair amount of self- contained touring in Australia and New Zealand and would appreciate first hand advice from others who have ridden these areas and of course locals.
thanks heaps