Off the top of my head:
First, you have to take the Disney bus from Pop Century to either Magic Kingdom or Epcot.
Then you need to take the monorail to the TTC.
Then you board a Lynx bus.
Then you have to transfer from that bus to another bus - the directions I've seen in the past indicate riding the first bus to downtown Orlando and transfering there, but a few weeks ago somebody posted a slightly less roundabout route.
Then you have to walk from the bus stop to the Universal Hub, and from there to the park entrance.
While I don't know how long it would take, it seems with all those different modes of transportation, and the transfers (and not even taking into account the wait time for any particular leg), you'd be using a good couple of hours at least just getting TO Universal.