I haven't ridden there in enough years that I won't give any specific advice. However, Prathman has posted information on routes that his club rides thereabouts over the past few years, so you might consider sending him a PM for some nice loops to ride.
Traffic or not, if I was hanging out in Groveland, I wouldn't be able to resist doing a mid-week morning loop of riding down the "new" Priest grade (non-steep switchbacks of 4.5 miles) and up the old Priest grade (same elevation change, but in two miles) a few times. It may not be your cup of tea, but if the traffic is light, it's a hoot, IMO. Then again, I have some hilarious memories of things that have happened there that makes it funner for me than it would be for others.