Here's the route I usually take -
You have to go through Diablo Country Club. Not because of safety concerns, but just to see the gorgeous homes. To take this detour, you need to find the hole in the wall while descending South Gate. It's a little hard to find - it will be on your right after reaching the area with homes; you make a sharp and steep right hand turn, then after about 100 yards of very rough pavement there will be a break in the white wall on your right. If you miss it, just continue on past the Athenian School and make a right on Diablo Road.
I normally take Diablo Road, right on Green Valley, left on Stone Valley, right on Danville Blvd. But, if you're looking for somewhere to eat you might just want to follow Diablo Road all the way into Danville.
From Danville Blvd head north several miles (there are plenty of strip malls here to find a snack). I hop on the bike path at the Rudgear intersection and take it all the way through Walnut Creek and over Ygnacio. If you're looking for food there's a Whole Foods right on the bike path, and you're only a block from downtown WC.
Staying on the bike path over Ygnacio, continue north a few miles until the path intersects the Contra Costa Canal Trail and turn right. You have a few options here. You can take the canal trail all the way back to Oak Grove, and then it's a mile or two from there back to Arbolado. Or you can turn into Heather Farm and take the Ygnacio Canal trail all the way back to Arbolado. Or you can do what I do, which is to ride through Heather Farm, cross Ygnacio at San Carlos Dr, and then follow the bike route signs back to Arbolado.
If I had any patience at all I would map this out on Bikely. Sorry. Here's a link to a map with the bike paths I mentioned - it does get a little tricky around Heather Farm.
Fyi in case you don't already know - if you park at the second lot at Arbolado, there's a bathroom and drinking fountain.
Have a great ride! I really enjoy riding both the north and south roads. The terrain and scenery are really quite different.