Loch Lomond reservoir is in the heart of Santa Cruz County. This is the major reservoir, and it is only open for fishing (not swimming). If you were looking for park information about renting boats and so forth, then you'll just have to search the Internet for pages put up by visitors; there used to be an official page, but it seems to be offline these days. You might try inquiring at the water department (remember, it's a reservoir) at the City of Santa Cruz.
Oddly enough, in all the years I've been here, I had never been to Loch Lomond, probably because I didn't have the urge to fish for trout. So I biked down from Bonny Doon to Felton, an exceptionally easy ride, as it is all downhill. At Felton, I went up to the Glen Arbor area, thinking that it was the quickest way to the reservoir. Wrong. The road from Glen Arbor (near Ben Lomond) goes over a ridge before coming down to Zayante Road. It would have been much easier to take Zayante Road directly from Felton.
From Zayante Road, the route takes Lompico Road, to West Road. This area reminded me of Snuffy Smith, Beverly Hillbillies, and similar environments. The property is worth a great deal of money, but you'd hardly know it from looking at all the rusting vehicles. It's worse than Bonny Doon, in that regard.
West Road is short but very steep, into Loch Lomond. I had to dismount and walk my bike up. Even pedestrians (and bicyclists) must pay a dollar to get into the recreational area (more for cars, of course). It's worth it. You can rent a boat, and the store sells soft drinks and snacks, but no real food. I hadn't come to fish, so I just walked around.
There are plenty of picnic areas (but remember, no swimming). If you have a boat, or if you rented one, then it is possible to picnic on an island. Keep in mind that since this is a reservoir, it's a big-time no-no to do what bears do in the woods.
On the way back, I stopped in the Trout Farm Inn for a beer. It's a famous name, but I'd never been there. Actually, the only reason I stopped is that I noticed a couple of local yokels (and I do mean yokels) with bottles of Coors and Bud, so I knew that it would be a refreshing change from the yuppie-student oriented stuff that I see back in Santa Cruz. Still, the cheap beer was almost twice what I'd pay for it in a local yokel bar in Florida.