The Direcway [Hughes] system will work for you in most of North America, including Mexico. Hughes discourages non permanent installation and requires that the service be installed by a certified installer.
I offer an RV adapter Kit which will work on any RV with an Awning. The Kit includes the Hardware for mounting, and instructions for how to work it.
If you purchase the Direcway service from me, I will assist you in setting it up.
Assuming you are in Arizona between April and October and have not yet purchased the Direcway service. The cost is $1200 in addition to the Direcway monthly charges.
For a view of the footprint of Satmex 5 go to
http://www.loralskynet.com/fleet/satmex5/sm5ft_us.asp