Try up the Arroyo Seco behind JPL
Trailhead: From the Foothill freeway (210) in Pasadena, take the Arroyo Blvd/Windsor Ave exit. Head north on Arroyo, which becomes Windsor. Park in a lot on the left about a mile up, just before the intersection with Ventura Street. Walk up Windsor a few hundred feet to a gated ,narrow, paved road on the right side of a Y. The road to the left drops down into the JPL parking lot. (Lat:34.19338 Lon:-118.16893)
Bicycles are ok. You can fish anywhere on the right side unless posted otherwise. I caught trout (Check Western Outdoor news for stocking dates) at a pond at Gould mesa and most anywhere along the way. I worked at JPL and rode up the canyon before work and caught a limit every time they stocked it. I look for the specific tire tracks of the stocking truck to find the best spots
I also rode horses with the resident ranger! It's about a 1.5 mi back. Water fountain at the ranger station. There's been no rain this year and it's pretty late in the season so the water may be down. Best bet is to call the local ranger for ANF.
P.S. Another hint. I've panned for gold up the Arroyo after a heavy rain. It's there under one of the bridges