Travelling around Alaska next year - Is it worth joining Alaska Mileage Plan?

We are planning on taking some internal flights in Alaska next year. Is it worth joining Alaska Airlines just to have a membership? We could then take advantage of their buying miles offers in the future perhaps?

thanks in advance!

I would say yes.  It can be a very lucrative program.  I once flew KUL-HKG-LAX(stop)-HNL, the bulk of my honeymoon, all in business class, by buying points.  Combined cost for wife and I, ~$2500.