If you can hire bikes here from a guy named Oscar Calderon. If you look at the Mexico Meeting page from 2005 or 2006 you should be able to find hisd details. A Swiss friend rented a Suzuki DR650 from him and had nothing but problems with it. He switched it for a BMW for about 3 days that was better. His bikes are the berst you can find here. They are also the worst you can find here. In fact they are the only bikes you can find here. He rents out of Mex City but think can take the bikes to other places. He rented a F650GS to a guy in Copper Canyon the last time I was there and the guy was thrilled with it.
If you need more info send me a PM.