I don't think anyone on this board could tell you. But what I can tell you is that more than likely, there are open spots in the dial. Almost anywhere in Mexico (Exceptions being the borders, Mexico city, Guadalajara, and Monterrey), you can find open spots on the dial. San Luis Potosi for example has the dial clear from 100.1 all the way to 105.7. Almost the same thing for Santiago de Queretaro (Both these cities are a little more than 200 km away from each other) I'm pretty shure you can fit at least two station in both of those major markets. Also, don't forget that the rules for Commercial stations are different in Mexico. This means that commercial stations can operate below 91.9 FM.
My question is, what does the U.S. have to say about this? I know alot of broadcasters will jump on this opportunity. If Mexico fills the dial, it will leave no space for U.S. broadcasters to move around or file for new stations. I'm not an FCC guru, but I'm shure the FCC will say something regarding this issue.