Yup, it can be pretty difficult to find stations in rural areas other than Mexican ones. Some of the music is decent, but the ads are usually frequent, long, LOUD, and often have this cheesy reverb effect that is campy at first and then just annoying. For my taste, it beats rap, but that's all.
The lack of variety in FM stations seems to be a fact of life now. It has little to do with Mexican, rock, jazz, county, or any other particular genre of music, and a lot to do with copycat station management who would rather try to steal listeners from whatever the local top-rated stations are instead of developing their own sound and their own market. So they all chase one market which becomes overserved at the expense of leaving everyone else out. If you like the musical "genre du jour" in your market, you're in luck. If you don't, too bad.
In a way it is much like the washer market, in that once upon a time customers could choose from a Bendix or Westy front loader, a Frigidaire Uni-Pulsa-Multi-Matic, a Kelvinator with the old ABC-O-Matic eccentric motion, or a conventional reciprocating agitator unit from Norge, Maytag, Whirlpool, etc. First the front loaders and Kelvinators went away, then the classic Frigidaires, and Americans were left with only the reciprocal top loaders. Now we're finally getting an option with new front loaders, but only because they are more efficient and import brands started selling them, not because domestic manufacturers actually thought some of us might prefer an alternative design.
I understand the need for profit and production efficiency, but when any market condneses itself too much Americans will always find an alternative. This is what is driving the growth of Sirius and XM, and if I spent much time driving outside of the city I'd sign up too.