Thank you all for the comments! I had a great weekend at Bolsa Chica, Huntington Beach, and Upper Backbay, Newport Beach. Not only did I manage to get some close shots of Skimmers (e.g.
http://www.birdphotographers.net/for...ad.php?t=12652) but I also got some first sights (e.g. Least Terns, Little Blue Heron, Leucistic Coot, and some UFBs), and in a few cases good pics. :)
As for Skimmers, both sites had plenty but mostly from a distance and/or just flying by from or to the nesting site. It was not until the last evening that I discovered a spot at Upper Backbay that allowed me to get low and close - well, sometimes depending on how close the Skimmers approached the shore.
Note, due to the rather unsettled weather this weekend in Southern California I stayed fairly close to the bridge at Bolsa Chica. It could very well be that there are other spots which are better for the Skimmers at BC.
Hope that helps future out-of-area visitors. Good luck! JR