Mexico for the most part is not difficult. You need to be patient as things happen slowly. A few tips here and there help. The amount of cash you need to bring, depnds on the aircraft and the hours you operate. After hours will be EXPENSIVE! After midnight in CABO is "Bend over Gringo" Note that you will get a better price on fuel if you use cash. About 4 - 5% minimum. Have not used handlers in Mexico for years, but there is usually someone around that will meet you and offer their services. Places like Cancun, Toluca, Cabo, PV, Cozemel and Alcapulo, you really don't need them. Some of the more remote areas, you might.
Knowing Spanish is nice, however, i have done reasonable well down there. And my Spanish is limited to:
Hello, Please, Thank you, Bathroom, Good by, My Spanish is very limited and One more beer, Senorita.
But you have been there before so it is not all that unfamiliar.
Have fun.