Boss,
You must watch to many scary movies or something. It's not that bad down here for critters. I would rather have a scorpion in my rv than a mouse. Snakes don't like people so it's unlikely that you will encounter one, especially in the fall when they start to hibernate. Scorpion stings are like bee stings so unless your allergic to them no worries.
I have lived here for 20 years and never heard of any special dog diseases. Sure their is parvo and such but that is everywhere. I also had a puppy and cat that survived a rattlesnake bite but we live in rural az on a three acre lot. Rattlesnake bites do a lot of damage so that is one you would not want to get.
Just have fun on your trip and don't worry.