Go to City Hall - as you face the entrance the door to your right is where you pay your taxes. You should have your tax bill. I paid by a Bancomer check - I might have been able to pay with a US check but I wasn't sure and I think they indicated a 10 day hold on it? Last year I paid by credit card but they indicated they couldn't do that. Not sure if that referred to just today for some reason or if it was a new rule. Cash is always easy but I never have cash with me.
It was very easy - I just handed them the tax bill, received a 15% reduction since I was paying the full amount in January, they told me how much I owed. The check was written and I received a receipt and was out of there. This year no line so it took me less then ten minutes.
They were all very nice and helpful.