New York City
How do I get around to take day trips from Medellin?
Can I rent a car, take a bus, or cab it?
It all depends on your budget and where you're going. Most day trips to pueblos such as Santa Fe de Antioquia, Guatapé or Jardin can be done by bus. Buses leave fairly regularly and are a fairly comfortable ride (if a little bumpy).
You can a hire a driver too, although I'm not sure how far they'd go or rates they'd charge.