Richard
The Mexicans are not the only source of electronic charts for the Sea of Cortez... Many companies will sell you raster or vector electronic charts.
With that said, in some places, depending on how far you go up the Sea, the charts will be inaccurate, sometimes up to a 1/4 mile off. This is because some of the Sea of Cortez has not been surveyed in over 100 years.
Find your electronic charts in the US. Once you are in
La Paz, ask the local cruisers were to
purchase the Sea of Cortez Paper Charts published by the Mexican
Navy. They recently did some surveys or
parts of the Sea and they seem to be more accurate than any other paper charts.
I didn't use raster charts, I used a
Navionics Gold Chip in my
Raymarine CHart Plotter, which was fairly accurate thought the Sea. When it wasn't, I would overlay my
radar on the chart and determine the correction. I also didn't carry paper charts up there and found I didn't need them. I made it all the way to Puerto Penasco (Rocky Point) on my electronic charts. They were also very accurate on the
west coast of the Baja.
I would also highly recommend Shaun Breeding and Heather Bransmer's
Guide to the Sea of Cortez and
Guide to Pacific Mexico. These are the
BEST guide
books for Pacific Mexico and will give you all the information you need, including chartlets,
GPS waypoints and local knowledge.
On a side note... I spent 19 months in Mexico before heading south, through the
Panama Canal, back to Mexico and eventually
Florida. I covered about 9500 NM from
San Francisco to
Florida and if I had to do it over again, knowing what I know now... I would never have left Pacific Mexico. It is some of the most beautiful cruising grounds we saw and much cheaper than anywhere else!!!
Good luck and have a great time