Where to Catch Out in Texas

Dallas
Kansas City Southern and Norfolk Southern run a non-stop intermodal train between Dallas and Atlanta. They interchange at Meridian, Mississippi. Trains operate Tue-Sun, leaving Atlanta at 4am (arrives at 1045pm), and leaving Dallas at 245am (arrives at 11am next day).
Austin
Catch out of Austin at the fourth street bridge over Lamar Blvd - right by the Amtrak station. Trains sometimes stop, most often don't, but are usually going slow to cross the bridge over the Colorado. Northbound trains go to either Dallas-Fort Worth or Houston (switching at Taylor or Valley Junction). Expect a long wait at Taylor. Southbound takes you to the border (Laredo) or to the coast (Corpus Christi), both passing through San Antonio.