From Mark D
Currently, Izzy (our older grey tabby) is allowed to venture outside freely, but Monty (the younger black-and-white) is still restricted to indoors. He sometimes makes a break for freedom, but usually gets scared and is happy to come back in. You won't have to worry about medicating either of them. We'll leave you contact information for our vet (good idea!) and a blank cheque should you need it. They do like to sleep with us, but you're not obliged to do the same : )
I've sea-kayaked with these outfitters before and they are great: http://www.aqua-adventures.com/. Kirstie and I did the introductory course together, and I also did a whale-watching expedition, although you're arriving a little late in the year for that. This calendar page shows everything they have scheduled for June: http://www.aqua-adventures.com/june.html.
There is a ton of hiking nearby and for a desert activity, Joshua Tree National Park is 2-3 hours away from either San Clemente or Oceanside. There are several day hikes you can do there, and even just driving the loop through the park makes for a spectacular day. We have camping gear if you feel like making it an overnight. I just left the kitties alone for two nights with lots of food and water out and they were fine. A little grumpy, but otherwise healthy :)