Brian: Until just recently I was a long time resident of Santa Fe and I can verify what you have said. Back in the 50s or so the Royal Academy of Madrid, which passes on all official changes in Spanish language, sent a team to northern New Mexico to study the local language. Why? Well, historically the Spanish came into northern New Mexico with the Conquistodores, and a small percentage stayed behind as colonists, and eventually concentrated in the western foothills of the Sangre de Cristo mountains and along the upper part of the Rio Grande River. But the nearest sizable settlement was in Chihauha, several hundred desert miles to the south. So these people were essentially cut off from the natural progression of the Spanish language for about 200 years, and they retained much of the language they brought with them from old Mexico. Hence the Royal Academy was anxious to have the opportunity to study the language spoken today as it retained (until the last 50 years ago) much of the structure of 16th century Castillan Spanish. I have been told that if you understood Spanish well, and listened carefully you could pick up the "th" traces of the Castillan accent.
I have been told by native New Mexicans fluent in the local Spanish, other than what I have been talking about, that they have trouble understanding native Spanish speakers from old Mexico, as the languages are so different. (You use the formal Spanish name for automobile tire in Santa Fe and you might be picking yourself off of the floor.)
Just to put a railroad spin on this, I got to know the Amtrak agent in Lamy, NM, who was Spanish. (Now I do understand a bit of Spanish, but I wouldn't call myself fluent by any means.) Bill was sort of a wheeler dealer type with business interests in old Mexico. One day I stopped into the station to say hello and Bill was on the phone conversing in very good Spanish, in contrast to the common Spanish spoken around Santa Fe. Anyhow, I told Bill he must be talking to someone in Mexico. He agreed and asked my how I knew. I told him, "Because you were speaking good Spanish".
