Last night our friends called an RV park in Mazatlán and were told we'd have no trouble staying at their park. Skittishness of tourists is one reason they gave, but they said the overall economy is the main problem. In any case it has security, has wi-fi, and is right by the beach. That way I'll be able to get sand in my toes, drink cerveza, maintain the Internet Review of Books website, and write blog entries accompanied by lots of photos.
Mexico is a beautiful country wracked in places by violence. Mazatlan itself is said to be safe for tourists; as with any big city, there doubtless are neighborhoods where strangers shouldn't go. But our friends, who've been there, tell us we'll get everywhere we want to go by bus or taxi.