We did this in December, but with only 2 people. Our taxi ride from the All-Stars to Royal Pacific cost us $30 with tip. We had a towncar to take us to/from the aiport, but really did not know if we wanted to do Disney for the day and go to Universal at night or leave Disney early and go to Universal for a full day (we have AP's for both parks, so admission didn't matter). It was much easier, I think, to just take the taxi for the same cost. You are running on your own schedule. We could eat a leisurely breakfast and transfer hotels with no problems at all and not have to worry about being in a certain place at a certain time.