I don't know about any groups coming in but the weather should be very nice. The high on Saturday is around 87 and on Sunday around 78 and then cooler for the beginning of the week.
But the following weekend, the World Cheer championships are over at Disney. All of the All Stars are full and some of the teams are overflowing into the moderates. SO, you will probably see some groups at Universal - but it won't be anything like the madhouse it will be at Disney.