Duncans Mills CA to I5 directions

At that time of day on a Saturday you should be fine taking 101 to 580 and then across the bridge and stay on 580 all the way to 5. I assume you're going in the Class A with the toad. So if you need to stop try and find someplace before you get to the Richmond bridge to stop and go to the potty. Once you're on the bridge you'll want to stay on the road all the way to at least the Livermore area. There aren't too many easy and safe areas to get off and on the freeway between those spots. It's a real congested area.