That's about a 90-mile trip; I would allow a little more time just to be on the safe side - - you never know with freeways and accidents.
Fortunately, for most of your trip you'll be going against the traffic so it should be pretty smooth. (15 South, to 210 West, to 605 South), but once you get on the 60/10 West you may have traffic both ways.
I always leave way early, especially if it's an important appointment. If I get there too early, I stop for a snack and a drink and read my book. Less stress that way. Good luck!