I did both at the same time, I couldn't wait to learn my 1st song. But I also recognized there was value in learning some fundamentals.

When I started 6 years ago, I was very regimented, which was probably good, but now its more organic. I work on what is most important at the time. I just spent my entire practice session on a song a group of us will be practicing tonight. Nothing else.

But looking back, I am glad I did at least some of the boring stuff. 

BTW, there is great value in recording yourself as your practice. Not your entire practice session, but maybe a scale or a section of a song you are working on. It's good to hear yourself played back. You will hear things you know you need to work on. I just use Garage Band on my phone, no fancy software.

Good luck 

Bill