Are they in the Santa Ana appreciation society, or on Aztlan payroll? :-)
Direct sources to debunk this historical revisionist lie:
http://www.loc.gov/rr/hispanic/ghtreaty/
"By February 1836, Texans declared their territory to be independent and that its border extended to the Rio Grande rather than the Rio Nueces that Mexicans recognized as the dividing line. Although the Texans proclaimed themselves citizens of the Independent Republic of Texas on April 21, 1836 following their victory over the Mexicans at the Battle of San Jacinto, Mexicans continued to consider Tejas a rebellious province that they would reconquer someday."
Hidalgo Treaty map
http://www.loc.gov/rr/hispanic/ghtreaty/ghmaps.jpg
Mexican Army was raiding and out right invading the Texas border prior to the war. This caused the American Troops there at the time to counter thus really starting the war before proper declaration. I think they are still sore over how we kicked their butt so hard when they supposedly had one of the best trained and experienced army. But who cares, this was a small war and was pretty much nothing more than a breading and testing ground for the coming Civil War.