PdC is too touristy for us, and IMO the beach isn't as nice as Tulum, but the shopping is fun, and there are a couple of good music clubs that get Afro-Cuban bands and salsa.
Try Yucatreks for small van trips to ruins and some of the cenotes.
Places to see:
Tulum beaches and the Sian Kaan biosphere are wonderful.
Swim/snorkel with huge turtles and rays in Akumal, another nice beach.
See Coba ruins by bike taxi.
Valladolid is a lovely Colonial town from which you can see Chichen Itza and Ek Balam ruins and a lot of cenotes. There's dancing on the plaza on Sunday evenings.
We've never gotten sick. And we eat in more local places than you're likely to. You drink and brush teeth with bottled water. PdC even has big US box stores for that kind of purchase.