If you are in bumper to bumper traffic, and you are going probably 20 mph, then I would say to go ahead & get it. But, at noon on Tuesday, you shouldn't need to use it.
I go to San Diego quite often (I'm kind of near LAX), and I've only used that toll road once when traffic was almost at a standstill.
If traffic is moving steadily, don't worry about taking it. The 73 loops around the hills and brings you back to the 5. It is not a shortcut, just a way to get around when traffic is really congested.
Traffic may also bottle-neck around Mission Viejo area, but there are no toll roads to bypass that. You just got to muddle on through.