I've seen dogs on the beach in some parts of Laguna. I don't know the laws, but here's an excerpt from the Laguna Beach Municipal Code:
6.16.020 Dogs on beaches, in parks and school grounds--When and where prohibited.
(a) In addition to the restrictions provided in Section 6.16.120, and except as provided to the contrary in this section, it is unlawful for any dog to be within the following designated beach and park areas within the city, and it is unlawful for any person, firm or corporation owning or having charge of any dog to permit or allow such dog to be within the following beach and park areas, whether or not confined by leash, at the following times:
(1) At any and all times within Bluebird Park, and within Boat Canyon Park between June 15th and September 15th of each calendar year;
(2) At such times and within those areas of Heisler Park as the city council may from time to time fix and designate by resolution;
(3) Notwithstanding any other provisions of this code, no person shall take any dog, whether leashed or unleashed, upon any public beach in the city between the hours of eight a.m. and six p.m. from June 1st to September 16th, nor shall any person owning or having charge, care, custody or control of any dog cause, permit or allow such dog to be upon any such beach at any time during the above-specified hours;
(4) At any and all times upon any public school grounds, dogs are prohibited, whether or not confined by leash, unless prior written authorization by school district is obtained;
(5) At any and all times in tot lots or play equipment areas of any city park or beach.
(b) The restrictions and prohibitions of this section, and of Section 6.16.120, shall not be applicable to dogs while they are enrolled and participating in obedience classes sponsored by the recreation department of the city, or to guide dogs for blind persons. (Ord. 1318 § 1, 1996: Ord. 1031 § 1, 1982: Ord. 943 § 1, 1978: Ord. 918 § 1 (part), 1978)."
Looks like they're not allowed on the beach during the peak summer month hours ... you might be able to do it before 8am or after 6pm. You can find the Municipal Code in it's entirety
here. Title 6 deals with Animals. Good luck !