Personally, I think I'd wrap my guitar in a zippered dry bag and stuff that in a guitar bag that I had weatherproofed with wax or silicone for good measure--it is going to be lighter and easier to carry than anything else--

for extra assurance, I'd make the guitar of choice a used Ovation or Applause--there is a good reason that rock bands use them on the road, they sound good, they are durable, and you can get another one anywhere, if worse comes to worse. Also, make sure your guitar has a built in pick-up--many of the musicians you come upon, especially blues guys, will be plugged in--

Travel and backpacking guitars would be great, but they tend to be either "paddle" guitars or short necked items, which will have a considerably different sound than you'd want, especially if you plan on recording--