I do think you can buy a boat in 'good repair' - at least reasonable - esp for the limited duty you describe on the Sea of Cortez (presumably with time to 'pick your weather window' for most passages)
There are no guarantees, unfortunately, as to surveys. The surveyor you get, how well (or whether) any issues are hidden, and general disclaimers of liability by the surveyor mean that you get your report and make the best of it. It's always best to be present during survey so you can get a more complete reaction besides the printed word, and a good surveyor will pass on all kinds of nuggets as the survey progresses.
But if you find the boat you like that's been looked after, and esp if you buy in Mexico I'd expect you'll find something... of course, double your budget and you'll find something better!