I highly discourage you from riding the rose bowl ride if you've only done one group ride. being fast is one thing, knowing how to ride in a pack, especially that fast is an entirely different beast. Even if you are riding near the back, you can still cause an accident, the good thing is that you'll take out fewer people. Basically as someone else mentioned, you are going to get accordioned and even if you think you are fast, you are going to get a completely different workout. What happens is you are going to keep on hitting the afterburners to keep up with the pack, you will sometimes get delirious and you might hit someone else's tire in front of you or to the side if you haven't already been dropped. Anyway, the people that do these rides are kind of agro and if you don't know what you are doing, they are going to give you hell. I urge you to practice riding in a moderate paced group first. Something like the 8am montrose group.