They're off of 30 and Beltline in Garland. It's a bit of a drive, but it's worth it.
They're website is
http://petmobile.com/
You should call and check out their prices. I know that most things are little more reasonable there than other vets. For instance heartworm treatments depend on the weight of your dog, same as spaying/nuetering. They also do mobile shot clinics and come through certain parts of Dallas on certain dates and offer the same prices for shots as they do at their walk in clinics. They also have clinic days where you can just come in and sign up to see the vet instead of making an appointment.
It can get crazy and busy in there and the wait might be a little longer than normal, but price wise its totally worth it and everyone is so nice and helpful up there.