Short Mexico Vacation

I'm hoping someone here has some insight on this. Can anyone make recommendations regarding vacationing in Los Cabos vs. Mazatlan vs. Puerto Vallarta? Girlfriend will be interested in shopping and since this is a birthday trip for her, that'll be important. Both of us will be interested typical beach stuff (swimming, day/night cruise, etc.), sight-seeing on land, eating, drinking (mainly me drinking).

I'm keeping an eye on travel.state.gov to make sure the drug violence doesn't spill into the resort areas, so don't worry your pretty little heads about that.

Thanks all in advance for your help.