This is regarding the Foothill/Niles Canyon/Palomares/Dublin Canyon loop, which is in the Dublin/Pleasanton/Castro Valley area...

I just scouted out the loop in my car at lunch and I've read it is a popular route. It looks like a beautiful ride with sections that don't have very many cars. 28.3 miles, just right for me.

I'm just wondering, what do people prefer on this one, clockwise or counter-clockwise?

I've done it many times in both directions. I guess I prefer it counter-clockwise, especially if it's windy. Dublin Canyon is a wind tunnel sometimes heading west.

The climb up Palomares is easier from the south. I used to always go that way because it got the Niles section done with earlier when there was less traffic.

Dont forget NORRIS Canyon
I go clockwise
start intersection of Niles Canyon rd and Palomares
then

Palomares north
Castro valley blvd West
right on crow canyon rd (north)
right on Norris Canyon (east)
right on bollinger canyon (east)
right (south) on san ramon valley - change name to foothill at 580 crossing
right on niles canyon blvd to complete the lo0p (approx 40 miles)

traffic spares for me because I go at 8am on weekdays
I love this ride

ps Norris Canyon East you can touch 50 mph for a few yards :)

heres a motion based map from yesterday (google maps, google earth, elevation, ...etc)
http://trail.motionbased.com/trail/invitation/email/accept.mb?senderPk.pkValue=13607&unitSystemPkValue=2&episodePk.pkValue=3931624

I say clockwise.

I prefer riding clockwise because its easier making right turns. Also, if riding clockwise I make a right on Laurel Creek Road off Dublin Canyon. This is a short steep residential street that will lead to bathrooms and water at the second summit, and downhill to Foothill. This will avoid the busy intersection of Dublin Canyon and Foothill.