The McAllen Foreign-Trade Zone (FTZ) is located south of McAllen between McAllen and Reynosa. Commissioned in 1973, it was the first inland foreign trade zone in the United States and continuously ranks among the most active FTZs in the nation.
Marigolds take around 45 to 50 days to flower after you plant seeds, so seeds sown in early April should flower by May.
This means that they will not survive the first frost of fall and will not come back in the spring, unfortunately. It would be best to let them die where they are, then clean up the spot and prepare it for the next batch of marigolds that you can plant in the spring.