Hey!

I've been to Caral and it's a bit of a drive from Lima. There are no cabs around the city that would take you to Caral and back. You would have to hire a tour, go in a bus or hire a private driver for the day. The citadel is around 3.5-4h away from Lima, and could be even longer.

Let me know if you want me to investigate further and I'll try to give you a hand with some local tour companies