I would aim for no later then 2 hours. Some times we have whisked through LAX in a very short time, other times the security lines are long..
I can't answer the shuttle question, we always rent a car... the drive is about 40 minutes if there is little to no traffic, but can be quite long if there is traffic.
The one time we used a shuttle to get to the Grand Calif, it was about 90 minutes to 2 hours just to get to our hotel from LAX... they had to drop off 2-3 other guys at their homes on the way.. after that we have always rented a car..