Sorry I didn't answer this before--Tex-Mex and Norteno, and Tejano refer to the same music, El Flacco Jimenex-style polka music from the Texas-Mexican border region--it is considered to be a traditional music form, since it has been passed down through a number of generations, and it continues to flourish today. The polka music was brought to the area by Czech and German immigrants from the end of the last century on, and it became intertwined with the regional Conjunto ballad traditions.
The Smithsonian Folklife festival featured several bands this year, and there is probably information on them at their website.Click here
Arhoolie Records has been a great source for recordings of both contemporary artists and for historical collections which you may find at: Click here They also have available Les Blank's "Chulas Fronteras" which is a great docmumentary about the music.
Salsa is the name given to contemporary Cuban-American dance music that is based on tradtional Afro-Cuban dance rhythms and also the ballad tradtion. Check out the Buena Vista Social Club film, and all the CD's that spin off from it if you want to hear some great music in this tradition.
The term "Hispanic" tends to be used more in the Western US, and is generally and loosely more tied to Mexican an Mexican American cultural things, "Latino" tends to be the preferred term in the Eastern US, and is generally and loosely associated with Cuban, Puerto Rican, South American culture and people.
There are so many different cultures and traditions that get lumped together in those two names--too bad that people in El Norte don't get to know them better--