Hi Marybeth,
Thought I'd reply to you as I recently adopted a 2yr old dog from an animal shelter, he didn't seem to have had any training either, and had been in the shelter for 9 months or so, however he has responded well to his training
Infact he learned as quick as a puppy, within a week he was walking to heel ( until we see another dog, but we're working on that!) He very quickly learned to wait before his food, etc. I would implement alpha training straight away, but for sure with patience an dedication, and of course fun he can be trained
have fun