Once you board the bus, the ride from Pop Century to Epcot should be about 5 minutes. But you might have to wait up to 20 minutes for the bus to arrive ... buses to each destination run about every 15-20 minutes.
There is no bus from Contemporary to Epcot. You'll need to catch the monorail at Contemporary, and then get off at the first stop, the Transportation & Ticket Center. Once at the TTC, you'll need to get off the monorail and go around to another platform to wait for the monorail that heads to Epcot.
You asked a monorail question in another thread, and in that thread I briefly explained how the monorail system works.