My understanding is that he has no cell phone and will never own one. It seems to me from the many interviews I've heard of him, that he goes there to "unplug" although I'd guess his son and daughter have a way of getting a hold of him.
Here's the quote on living in Baja. His wife has some sort of ailment that makes it hard to stand the winters in Minnesota.
Regarding his life in Mexico, Ventura said, "I live one hour from pavement and one hour from electricity,..." "I drive down and back every year and it's truly an adventure to live down there where I do, because I'm off the grid,..." "I have electricity but it's all solar. I'm completely solar-powered down there. And it makes you pay more attention. It makes you turn the lights off when you're not using them."