If you want to limit yourself to going no further than Rocky Point for liability only, that's fine. I found it economical to purchase liability, comp and collision right in Rocky Point on an annual basis. Mexican insurance is cheaper if you purchase it in Mexico without the hassle of changing US companies or going through a US broker. I found it much more worry free and economical than any way I could purchase equal coverage in the US. I totaled a vehicle in Sonora, and everything was covered as stated in the policy. Payment was in US dollars, no hassle.