As the owner of a service dog for my diabetes. I have it under better control now, so I don't need him, so he is "retired". I did a lot of training (about 6 months of intensive (2-3 hours/day, both of us get tired of that) training, and regular "less intensive" training (20-30 minutes/day) daily after that.
http://servicedogacademy.com/wp/training/coopers-puppy-manners-impress-seattle-diabetes-crowd/
(He's the brown one...)
Anyway, here's what I do on airplanes when I see a "Service Dog" on the airplanes, I strike up a conversation with them, and then ask what service the dog provides. So far, I've gotten:
"Oh, he's just a pet, and I just say that so he gets on for free."
"He makes me feel safe"
"I am scared of flying, and he calms me down"
"He's my therapy dog"
Then, I inform them that I have a Service Dog, and what they're explaining to me is a "therapy dog", and has no legal rights in the US.
http://www.ada.gov/service_animals_2010.htm
You can't take a "therapy dog" anywhere with impunity. You can ask the shop owner if you can take them in, but s/he can simply say, "no", after asking you the two questions on the form:
Is that dog required because of a disability? (Horses have stricter rules, and I think anything but a first class seat area would accommodate them, due to the physical mechanics of a horse.) For me, the answer is: Yes.
What service has the dog been trained to do? He senses when my blood sugar is going low.
On my last experience with grandma (someone else's), she got really quiet after I told her that I have a service dog (he wasn't with me on the trip to Mexico - it was a 3 day trip, and Cooper is out of it the first day of travel, so he wouldn't have been much help anyway), and I don't appreciate people that make it harder for me to travel with mine.
After getting off the flight, I had to wait on the jetway for my baggage, and two attendants appreciated what I did. Especially after the dog crapped in it's diaper.
A few things (yeah, I'm on my soap box):
Service dogs have to be well behaved.
Service dogs aren't pets, so please ask the owner to pet them. Many people that are blind (my sister in law) understand that people like petting dogs, but while they are working, petting them doesn't help the situation at all. Cooper loves the attention (and diabetic alert dogs are working 24/7, so the only thing he needs to do is alert me, whether he is being loved on or not, so I let people love on him. Both like it.), but when I give him the command to come to me, he stops, and immediately does so.
OK, off the soap box now... gotta pet the dog.