The border crossing from Mexico at Santa Elena into Belize is now much faster and easier as they are building a new border crossing. As you drive down to the border take exit signed “A Belice por libramiento”. This is the new border crossing. As you approach there is a drive-through for Mexican immigration where you will get your passport stamped. After that pull forward and park somewhere on the left and enter the group of big buildings. When we were there in Jan 2014 the buildings did not have signs on them, but you are looking for the Banjercito where you will cancel your vehicle permit. The process on the Mexico side is painless. After crossing the bridge the road makes a big turn and you will see a small white/green shack on your left, stop here! This is the fumigation building. Again when we were there, the building was unsigned and we drove right past it. Stop here and get your tires sprayed and get your receipt. Then drive up to the border area and park and the left and go into the entry hall to obtain your visa and your vehicle permit. The driver drives through the gate and picks up the passengers on the other side. Just a few 100 m down the road you will see a large white building for Belize Insurance. Stop here and buy your insurance and then you will be on your way.
The new border crossing is much smoother and avoids all of the people hassling you to buy insurance. Do not buy insurance until you cross the border and stop at the insurance building.
You are not allowed to cross to Belize with fruits, veggies, or alcohol so make sure you finish everything before you cross. That being said they never searched our vehicle.