The safer way to turn into LM is to pull over to the right hand, dirt shoulder, across from the new "LA MANZANILLA" sign, with your left turn signal flashing. Then, turn left when both north and south bound lanes are free of traffic and it is safe to do so..
Your left hand turn signal has two meanings down here: (1) you intend to turn left at the next opportunity, or (2) it is safe for the vehicle behind you to pass. You can imagine what mischief this dual message causes when folks try to turn left while on the highway, rather than from the right hand shoulder.
It's all part of the "fun" of driving in Mexico!