Hi KateJack,
I visited Puerto Vallarta and Mazatlán last year for the first time. If you are up for a walk, I find these cities easy to navigate to exploring touristy attractions.
I followed a 5-mile route to see some landmarks, beaches, art, and more.
If you are interested, I wrote two articles on my personal blog (see links below)
Puerto Vallarta
Mazatlan
Enjoy your visit!
Marie