I stayed a hotel adjacent to the SR 509 expressway and took a look at it from the SR 99 (International Boulevard) bridge above it. Unsurprising, the south end has no exit number, the overhead I could see simply showed I-5 South Left Lane - SR 516 Both Lanes. There was no visible signage for 24th Avenue S, so no exit number at this time.
I also did not get the opportunity to drive it as
tolling commenced on September 29, and we did not buy the expensive toll collection option Avis offered on our rental car.
Adding to the GSV link posted previously, the concealed portion of the overhead for Exit 150 shows Toll Road:
