Where is the cemetery gate in El Moncho?

Find the red handle then go and he will tell you to go and jump up on top of the graves where the arrow is pointing and throw the red handle at him.

The cemetery entrance is the gate to the left of the police station/jail (that you started in) in the Town Square. You have to approach the gate and Romero will appear and open the gate for you.

Actually the cemetery gates are down a path after you go through the gate taking you outside the town. The first time you approach this gate it is closed and Romero (as he agreed when you gave him his harmonica) will open it when you get close to it. You will find this gate at the top of the the Town Square (to the left of the jail). The Square is where there is a well in the middle and the Mystery Machine is parked in the lower part of the square.
After you leave the town through this gate, you go along the road, through a gate and past a couple buildings, you will find you need to have Velma turn on a front loader parked in a dug-out place in the road. You will use this to climb up in order to get up onto the continuation of the cemetery road that towards both the new and the old cemeteries. The new cemetery is the first gate you will see and the old cemetery can be found at the end of the road, gate is the last thing on this road.

It is on the left side of the jail. There is a big door where Daphne's pole is.