I made enquiries about renting an aircraft to take into Mexico last year but I was unable to find anybody who would rent me an aircraft. I even offered to leave a deposit equal to the value of the aircraft but the answer was still NO! It seems that there is a fear by Americans of flying into Mexico.
If You do manage to rent an aircraft, I would be pleased to learn of it and I know of a couple of nice airstrips over the border too. The other problem is that a lot of airports which are not hard tarmac are out of bounds for rented aircraft because of insurance limitations.
I have driven down to the tip of Baja and it's a nice drive with some very interesting places.