The text of the Treaty of Guadalupe Hidalgo seem to have allowed Mexicans living in California and New Mexico to make some choices: (1) leave or stay and (2) become a US citizen or remain a Mexican citizen.
"Those who shall prefer to remain in the said territories may either retain the title and rights of Mexican citizens, or acquire those of citizens of the United States. But they shall be under the obligation to make their election within one year from the date of the exchange of ratifications of this treaty; and those who shall remain in the said territories after the expiration of that year, without having declared their intention to retain the character of Mexicans, shall be considered to have elected to be come citizens of the United States" Treaty of Guadalupe Hidalgo
The bold part above says they will keep their rights as Mexican citizens, even in the USA. How would that have worked? Did that mean, even if they were in the USA, they were still protected by the rights promised them in Mexico's Constitution of 1824?