Transferring t$ to t4S is usually a breeze. If your first flight is not delayed, you should be able to make it given that it's late night when the passport control line should be short. However, I agree that it's a risky proposition that your first flight can't be late. Whetehr you want to act now or take a chance depends on how important it is for you to make it to MEX on time. If you have an important event to attend, I'd adjust the flight now. If you're not in a hurry, I'd take the chance and even pray that my first flight gets delayed so that I can have compensation.
