Hi Juan,
I'm a new guy to the forums also, but been hunting for long time. Public land hunting can be tough in So Cal, but if you're willing to do some back-country hiking, you can get to some pretty great areas. Your first order of business is now that you have a license, you'll need a tag if you want to hunt deer. Go to the CDFW wesite
https://www.wildlife.ca.gov/Hunting/Deer and look at the map to figure out what zone you want to hunt (D-16). The draw for all the premium hunts is over, but there are still some tags left for some zones.
https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=30896 There are still some D-16 tags available as of today.
Next you'll wan to get some maps and/or a hunting map app. I personally like to use the old fashioned paper maps along with the newer technology. Your best bet is to get a set of BLM maps for the county. You can get BLM maps here:
https://www.blm.gov/site-page/media-center/public-room/california/public-room-maps-sale You'll also want a set of National Forest maps. Go the the Forest Service Office in Rancho Bernardo for those. Spend lots of time looking at the maps and looking at Google Earth. Find your access roads. Do a sh!t load of driving and figure out all your access points. Lastly, get out there and do some hiking. Ironically, although I've been hunting for a number of years, I got drawn for an area that I have no experience in, and I posted a question very similar to yours yesterday. And I knew the answer before I even posted the question: Get out there and look around.
At the risk of pissing off the rest of this forum, here are just a couple well known SD County spots: Palomar Mountain, Palomar Divide Truck Trail, Lusardi Truck Trail, Black Mt. Road, Eagle Peak Road and Boulder Creek Road. And those are just general areas to get you to a trailhead to get into the back country.
Anyway, good luck and I wish you a fun, safe and successful season.