No one can really tell you if you should or shouldn't get one.
I got my first one when I was 16, I graduated HS early so I was already out of school. I went through a couple periods where I was fairly irresponsible. I was working and going to college part time and then I would go out with friends so my dog was left with my parents a lot. Everything worked out in the end though, I still have my first one plus another and I just balance my schedule between them, school, and whatever else...
It sounds like you're already thinking ahead about everything you would be taking on, so if that's what you want then go for it.
But I agree that summer time would probably be the best time to do it, that way you have plenty of time with the new puppy before going back to school.