I ditto the suggestion for a taxi or a town car. Depending on how many people are in your group, it may be about the same price -- or maybe even cheaper. Mears will have a set schedule of departures -- when we were there, there was only one time available to get to Universal in the morning. There'll be other people in the shuttle with you. You'll probably stop at other resorts to pick up additional people, and could stop at Sea World on the way there or back.
Taxi fare is the same regardless of how many people are in your group. (If you've got too many for a car, get one of the mini-van ones. The fare is the same.)
Also, if you want to shave a little off the taxi fare, you can take Disney transportation to either Downtown Disney or Saratoga Springs Resort. These are the closest locations to Universal, and there fare will be cheaper.