@ehBeth,
To transfer money from the US bank from the Mexico bank involves a transfer which is cumbersome, involves going to the bank in person, and involves a fee that would more than negate any benefits of transfering the maximum limit you can do. If you were transfering a smallish amount, let's say a couple of thousand, you would lose money on the U.S. side, not even counting if the fluctuations are in your favor.
I'm sure for large companies it's advantageous, but for an average person, any potential savings is hardly worth it.
This is where being an American shows. I really don't care if in the conversion of buying a shirt or bottle of detergent or something ends up costing me 10 or 20 or 50 cents usd more. Because in the big picture, everything costs so much less. In the course of running around in a typical day, you end up tipping various people 5 or 10 pesos here and there for really small things, like bagging your groceries, or "helping" you back out of your parking space, or pumping gas. For me, it's a quarter. Change sitting in the coffee holder in the car. For the kid who bags your groceries, it's money he or she brings home to their mother, who spends it on food.
Yeah, on paper it seems you would be interested in transferring money at the exact right time. However in practice for day to day items it's not worth thinking about. Now, if it were a bigger ticket item, I compare.
Honestly, it shocks me more that people in the States go out for lunch at work and spend $10 for a burger, fries and soda. For junk.
Re my original question, although I'm really thankful for the answer, and now have it straight, in practice it's really all academic. While there, I still have to buy gas, food. Where the big savings come in is the price of things like car insurance, property taxes, medical insurance, all of which cost like $300 to $400 usd a year. That's right. My property taxes on a brand new, 1400 square foot house with a roof top terrace, in a gated neighborhood is less than $400 a year.
This is basically what I see from my rooftop....