With only 24 event cards, the Mexican units advance as follows:
11 - Reserves (46% up to 58%)
11 - Morales (46% up to 58%)
10 - Cos* (42% up to 54%)
10 - Romero (42% up to 54%)
8 - Duque* (33% up to 46%)
* Susceptible to being disordered.
It should also be remembered there are two cards which cause potentially two random tracks to advance and another card which causes all units in #3 and #4 spaces to advance.
All of the units have a battle strength of 3, except the Reserves with a hefty 4. Aside their position on their tracks, their potential to advance ought to be considered when directing fire.
Ideally, the Cos and Duque units can be disordered early in the game to maximize impact. If you can pull it off later in the game, that is fun. But, chances are you'll have more pressing priorities with Mexican troops scaling the walls of the Alamo.