I'm certainly not an expert on
buying a boat in
Mexico (I'm in the US) but did look in to it last year. A very reputable
broker in
La Paz (also Matzalan) told me that there is a 100%
legal way to buy a
boat down there without paying Mexican
import fees. You'll need to check that out. I would recommend that you don't try and do anything illegal in any case.
I would bet
money, though, that many surveys have been done by US surveyors in
San Carlos without any problems. I would also bet
money that it would not be looked at well by the authorities. Lots of things are done down there the way they are because there is sometimes no other way to get it done (well).
Good luck.