I would recommend a rescue as well. I've now had three (dogs, and countless cats!) and they've been great.

Another thing to consider is that if you want to run with the dog, you might be better off getting an adult dog. I think it varies by breed, but there are recommendations about when you should start taking a dog for runs with you because it can be detrimental to their joint development. Also, if you are thinking endurance running - you are probably better suited to a dog breed with a long snout than ones with short snouts (like bull dogs or boxers) as the longer snout dogs tend to handle extended workouts, panting and temperature regulation better than short snout dogs.

Do a search on 'running/training with a dog' and you'll see tons of resources and information that would be worth reading before making your choice.