There are alot of personal choices that you need to make before you come to that decision.
I don't know your situation or your dog experience, but it seems a little hasty.
For me, getting a dog was a very long decision due to several different factors, such as our current dog, our finances, how much time we had to spend, what we were looking for in a partner and what we weren't willing to sacrifice... and then we made a decision and got our puppy.
Then, the whole process of getting the puppy took from July of 2009 to Jan. 29th of 2010 until we finally got the puppy.
But, we decided on getting a purebred puppy from an excellent breeder (which, is how you should do it if you're getting a purebred puppy) so it took quite a bit longer then going to a shelter.
If you do get a rescue dog, my suggestion is to get a dog that is currently in a foster situation so that you get some feed back on how the dog responds to a family situation. Sometimes, dogs are totally different in a shelter then they would be in your family, and you don't want to have to bounce a dog all over the place just because you didn't research.
But, I pretty much echo what the other posters are saying. Think about what you want- a family friend, a performance dog, a working dog, a show dog (some dogs can be all of these things) or do you want to rescue a dog from a shelter that may have not otherwise gotten a home?
Do you want an older dog already house trained or do you want to take the responsibility to raise a puppy? Puppies are tough!! It's like having a toddler in the house- maybe worse sometimes then a toddler.
There are sooooo many pros and cons to both. That's why it's such a big decision.
For us, we didn't want to take the chance of our current dog not accepting the "new arrival" so we opted for a puppy b/c our current dog is more receptive to puppies then older animals.
We don't have kids, and we both have flexible schedules, so for us getting a puppy was a natural choice.
I wanted a very stable dog, so we decided to go to a breeder that is well known for breeding for health and temperament first, everything else second.
Anyway, good luck and keep us updated with your decision.