as most replies have stated there is no tried and true answer but from my experience..... DW and i travel with 4 small dogs. a mini doxie, 2 chihuahuas, and a chi/beagle mix who is 15 yo. the 2 chis are rescue foster failures. DW and i have fostered for a chi rescue for over 5 years. they were considered special needs because of their puppy mill background. huge trust issues. thats why we adopted them after 2 years with us. they have become very sweet and loving dogs. they love be with us on trips. i always personally introduce myself to camping neighbors and ask them to notify me if our dogs ever become an annoyance by barking inside rv when we are off site. 3 years later to date no one has ever complained. we leave radio on when we leave camper for background noise, and normally aren't gone more than 3 or 4 hours. they have always traveled great. they are great watch dogs and will bark if they hear something unusual and they have extremely good hearing except for the 15 yo. i like this, no one will every break into my home or rv while im there without me knowing it.
working in dog rescue myself i can say one benefit of adopting an adult dog from a rescue that utilizes foster homes is that the foster home can give you a pretty accurate description of the dogs personality. our rescue adopts dogs on a trial basis. to make sure the dog is a good family fit before adoption is final. from time to time things don't work out and another dog is tried.
best of luck on the search.
