Here are the 2010 testing results for secundaria schools, which means that many of the same students tested will now be in prepa at your son's grade level:
These are the private secundaria school ratings from 2010, and some may not offer prepa education or be bilingual education: (if you scroll down on the same rankings, the public schools ratings follow the private schools ("particular" at the top right corner of each page). At the end of the data, there is also the number of students who attend each school.
This might help you narrow down your search for a school. In the top 10 (out of 262 schools rated) private schools in Jalisco, 6 are located in Zapopan:
#1 Centro de Desarollo integral Arboledas
#3: Instituto Anahuacalli
#5: Colegio Aleman de Guadalajara
#7: Instituo Miguel Angel de Occidente
#9: Colegio Cambridge
#10: Centro Escolar Los Altos
Here in Queretaro, preparatorio school fees at a really good private bilingual school run about 65,000 pesos (= US$5000) per school year including books and fees. This school is on the Cambridge system and is highly rated.
Good luck in your search.