Traffic should generally be OK except in a few bottlenecks which is usually where the freeway intersections are located.

However, with respect to carpool lanes on the 91, I believe in the "91 Express Lanes" tollway section, you can't access them unless you are a FastTrak member. It's 3 people or more in this section to qualify as a carpool (and then it's free) or you can pay the toll. However, I think you can't access it at all without the transponder.