Hi everybody and thanks to the many people who answered my message earlier today.
I went to Claremont Canyon in the afternoon and, with very detailed instructions, had no trouble finding the spot where the summer tanager had been seen. I stayed there for a couple of hours (from a little after 3pm to almost sunset) but the bird did not show up. In the very nice weather I enjoyed the acorn woodpeckers (up to three) thinking that the oak tree is their private property, often chasing the Nuttal's woodpeckers that try to feed there also. Other birds I identified include bushtits, oak titmice, Oregon juncos, California towhees.
I thank also the people that volunteered to show me around during my stay in Berkeley (which is about ten more days). I am not sure about my week-end plans yet, but if I'll have time for birding I'll get in touch with some of you.