iwillride.org 3/8/16:
Foothill Gold Line from Pasadena to Azusa Station & Parking Guide
Since passenger service started, the parking structures in Azusa have been filled to capacity by around 7 AM. Riders should know that other stations with parking have availability. The Irwindale Station is a great alternative for riders coming from the east. The station is located immediately off the I-210 Freeway at Irwindale Avenue and has had availability of parking this week. Below is a guide to help navigate to the Irwindale Station and other Foothill Gold Line stations.
Go here to see more.
It appears that the new extension is a victim of its own success. When new lines open, the new endpoint stations draw the most passengers since they will serve people who will drive from locations not reached by the rail line. I am sure that Sierra Madre Villa station in eastern Pasadena (the former endpoint) saw a reduction in usage since people east of there now have stations closer to where they live.