Actually, now that I look at the GSV, they sign eastbound 10 for Pasadena. I wonder where one would go from there. 605?
They are definetly messin' with your mind there.
Let's look at the alternatives.
Closest interstate in that direction is I-605. But that really dumps you too far east of Pasadena in Arcadia. You can backtrack to I-210 to get back to Pasadena however, but a very inefficient routing.
Closest state route is 19. A little closer to Pasadena, but still pretty far east of downtown.
Atlantic Blvd, even closer, but is confusing because street changes names to Los Robles, and has no numeric routing signage.
I think this is a much easier routing from there:
I-10 West to I-5 North to CA-110 North. This is the closest all "Freeway" connection (if you can call Arroyo Seco Parkway, aka Pasdena Freeway, a freeway) one can make from there to downtown Pasadena
Valley Blvd to Fremont blah blah blah (Going this way makes the NIMBYS upset)