Just a note about the rain. If you have the opportunity to ride through there while it's pouring you'll get quite the treat.
However, you've got to be mindful of the river crossing right after Tortilla Flat. Sometimes with the flash flooding it can get impassable. DAMHIK.
So if you're going to venture out in the rain I'd recommend taking the route counter-clockwise. Just to get that part out of the way first.