Coming north on I-5, you'll go through Stockton, then after about 8 miles, you'll pass the "Eight Mile Road" turn-off. Continue to the next turn-off which will be HY-12.
The Hy-12 exit is clearly marked. There's a "Flag City" RV resort there, a McDonalds, a Flying J travel center, etc. You really can't miss it. Head west a few miles to very tall bridge at "Terminous" , The Tower Park turn-off is just before you go over the bridge, it too is clearly marked.. If you travel a few more miles, you'll cross the second bridge over the Mokelumne River. Immediately past the bridge, on your right will be the turn-off to the Delta Loop. It's a 8~9 mile loop that has several Marinas and campgrounds.