http://home.earthlink.net/~ejlmp/sanmateodp.html

A new dog park is opening in San Mateo on June 4, and I'll be attending a Peninsula Humane Society mobile adoption from 11am to 2pm. Come with your dog, and / or come to check out our dogs if you have room in your life for more dogs. :-)

Here are directions:

Take 3rd Ave east (towards the bay) Stay on it as it curves around and
turns into J Hart Clinton Dr. They won't be allowing left hand turns
into Seal Pt. Park, so go up to Anchor Rd, and make a u-turn. Seal Point
will now be on your right and you can park in that parking lot. The PHS
van will be situated right by the dog park.