We stopped in Joe's while on a roadtrip one weekend and are looking forward to returning. The exterior is very unassuming - looks a little like Denny's actually - but the food and the service were a great surprise. We hunkered down at the counter and tied into some good comfort food - I had an omelette and my husband had grilled cheese. With his sandwich he had the option of french fries or ravioli - sounds odd, but he of course went for the ravioli and couldn't stop ooh'ing and ahh'ing. I did the same when Joe himself brought me some fresh salsa that he had just made - it was delicious with my omelette.
Pros: Diner-like ambience and food
Cons: Too far from SF!!