Yes, they also go to SeaWolrd for $18 PP r/t.
Check out this page for info:
http://www.mearstransportation.com/pdf/Rates2009.pdf
I've always made reservations the night before either from my hotel room or, if I remember correctly, at POP there was a Mears direct phone in the lobby that you could use. Just remember that, at least when we went to Universal, you had to call 2 hours before you wanted to be picked up & brought back to WDW, so remember to have a cell phone & the Mears number from you transport slip handy!