There's lots of options for free car camping in LPNF campgrounds, if that's easier, off Hwy 33 behind Ojai and along Paradise Rd in the Santa Ynez Valley off Hwy 154 just inland from SB. There's also car camping spots in the Upper Santa Ynez River area but they're a little bit more of a drive (from SB area, take Gibraltar Rd up to East Camino Cielo and follow it down to the Santa Ynez River by Juncal Camp and Pendola Station). There's also car camps farther into Santa Ynez out along Happy Canyon and Figueroa Mountain Rds- these probably all still fall within your 1-2 hour driving window.
If you wanted to hike in and camp, you could park your car at the Piedra Blanca TH parking lot and hike into the Sespe Wilderness (inland from Ventura/Ojai). Water's getting scarce but Piedra Blanca Creek is still running. It's maybe ~3 miles or so in from the TH. Another close-by option would be to hike up the south fork of Matilija Creek from the TH on Matilija Rd. There should be water there but it's really dry this year, so no promises. Be careful for break-ins at both of these locations.
There's a few camps in the Ojai frontcountry that have pretty reliable springs, but most don't make the best campsites. The Pines camp on the Horn Canyon Trail leaving from Thacher School in Ojai is probably the nicest. It's about 5 miles in from the TH though.
Closer to SB, there's a few places where you could park along Camino Cielo (the ridge road on the top of the mountains overlooking SB) and either hike into a backcountry camp, like Forbush Flat (bring your own water, the creek will be dry), or just discreetly stealth camp in a clearing off the road.
There's options for short hikes into the camps from various points along Paradise Rd and Happy Canyon Rds out in Santa Ynez as well. Just plan for dry camps.
Check out www.santabarbarahikes.com for more ideas or shoot me a PM.
EDIT: There's also lots of state park campsites but it'll probably be difficult to score a campsite on a Friday/Saturday without advance reservations. Still, you could check online for last minute openings at Emma Wood State Park, Carpinteria State Beach, El Capitan State Beach, and Refugio State Beach. These have showers, etc. and cost money to stay in. I think there's also camping at Lake Casitas out by Ojai.