Is Baja California safer from Cartel Violence due to its relative isolation from the rest of Mexico?
You got the 'relative isolation' part right. There is no city more far away (straight line) from the Capital (Mexico City) than Tijuana.
Tijuana is closer to Vancouver, Canada (across the US States of California, Oregon, Nevada and Washintong) than it is to it's own capital, Mexico City. Similar thing happens with other Baja cities such as Ensenada and Mexicali. Interesting, huh?
In any case, that could be said of the Yucatan peninsula.
BC, while far away from central Mexico, is right besides the US border. Millions of dollars in drugs are smuggled across the California-BC border.
That said, as long as one cartel has undisputed control of the drug traffic in a certain area, things tend to be calm there. That's why Mexicali is probably the most safe border city while Tijuana became a battlefield when the Tijuana cartel appeared. (Tijuana seems much calmer now since the Tijuana cartel became much weaker and the Sinaloa cartel took over the zone. Sinaloa cartel has had strong control in Mexicali since decades ago.)
The "War between Cartels" is because they wan to control the Border Towns, more specifically the Border Towns next to USA, the Three biggest Borders from Mexico with USA have some kind of problem because of the Drug Cartels.
The Biggest Illegal Drug Consumer in the World is USA! USA! USA! so cartels want control of Borders with USA.