How do I settle down here in Mexico?

If the pension can be sent to a non-US bank account - that is one option.
I have a pension and rather than incurring fees for wire transfers, I use the ATM to get money as needed.

You'll find Charles Schwab HY Checking account is popular among people who are outside the US. That is what I have. If you have a Schwab Investment account (required to get the checking account) with more than $500 USD in it, there is no fee. And when you use any ATM in the world they will reimburse you the fee charged by other ATMs.
Of course, you'll be getting pesos from the ATM and I've found that the exchange rate is very competitive and likely better than you'll get if you wire the money.
You'll have a withdrawal limit of $1,000 USD a day. If the ATM you go to limits you to 6.000 pesos then you can go to another bank or try again at that ATM and get more up to the equivalent of $1,000 USD.

I have had few problems with Schwab and each has been dealt with quickly and efficiently. You can't bear poor customer service when you are outside the US trying to get your US money out of an ATM!!!

So my short answer, now that I've given the longer one, is to open a Schwab checking account, deposit your pension there, and use the ATM to get the money you need. This works great for me.

She needs a resident visa. Permanente or temporal.