I crossed at Chautemoc, Mesilla in March 09 and I found it very pleasant.
The mexican Aduana is a little distance from the actual border, can not remember but maybe 5 km.
When you get to Messilla Guate. it is a very busy street with lots of pedestian traffic, just push on through slowly, the actual border is on your right. They will fumigate your bike tires first and then you can do your paperwork, which is inexpensive and quick!
There are money changers on the road, just know the exchange rate and use one of them, they are easy to deal with.
!Speak as much Spanish as you can!
The road from Mesilla to Hue Huetenango is great with lots of high topes,Hue Hue has lots of Motrocycles in fact it is crazy busy with bikes!
I stayed just on the edge of town near the McDonalds for about 30 dollars.