There is a Lynx bus #50 it makes one pickup per hour (around 50 mins after the hour) it will stop at Sea World or near Sea World, You can then change buses to get to Universal. this is the cheap way of getting there Mears can charge alot for a 2-way trip. If you go this way be sure not to stay late past 9 pm at Universal as they don't run the Lynx buses past that time.
also Check the Lynx Url above for the number route that you need to change to from the #50 route, as I don't recall that number.