We used Mears. Approximately $13 RT per person, cash only to the driver. They pick you up at your resort.
The day before your wish to go to Universal.........
Use any house phone or your room phone at WDW and dial "0". Ask to be connected to Mears. Tell the Mears operator that you want to go to Universal the next day, approximately what time you wish to leave, how many in your party, and your resort.
They will give you a pickup time on their schedule.
The next morning go to the front of your resort and ask bell services where Mears picks up and wait for the van or bus.
When you pay the driver, they will give you a return ticket with a phone #. You may schedule a pickup time when you are dropped off or just wait until two hours before you are ready to leave Universal and give the phone # on the ticket a call. You can use a cell phone or pay phone. Universal "might" let you use a house phone, but not sure about that.
Once you get your pickup time from Mears, proceed to the location where you were dropped off and wait for the van or bus. You will be returned to your resort!
Also, the standard Mears buses/vans show up at the Universal pickup area on a regular basis. If you want to leave before your pickup time, it is fairly easy to get on the next bus/van that shows up if it is not full already.
We were using the handicapped accessible van, so we had to wait until our pickup time, which was fine with us.
Carol