There are few if any "migrant workers" in the Palm Springs market. And migrants don't get diaries. Neither do undocumented immigrants.
What is a major factor is that the Palm Springs market is 54% Hispanic and a large percentage are first and second generation. Agriculture in the East Valley and the hospitality industry and the huge number of affluent retirees give lots of employment opportunities where knowing good English is not needed.
In the LRGV (Lower Rio Grande Valley) there is a very small number of first generation Spanish dominants. Most families there go back many, many generations.
Palm Springs is a mediocre to bad radio market, with low revenue and too many stations. The English language stations are, to me, not listenable. I use Sirius/XM instead for English language radio and streams for good Spanish language stations.