I'll soon be in San Diego, and have heard there are or will be new laws regarding ammo sales.

what are they?

Beats me.  I'm stocking up some now.  I know they are changing but not sure.  Going to be ugly, useless, probably unconstitutional and the state has probably screwed up the process for administering it as well as the requirements for Joe Citizen to buy, too.  (Short answer, I haven't looked recently.)  Currently you can still buy over the counter and everything is pretty much behind a counter or barrier of some sort, not much self serve.  That changes, I think, Jan. 1st but don't really know.  Haven't started to panic yet.

If you are driving in before the end of the year, bring what you can.    Calguns.net should have more specific info.  But I can't find it.  Finding what should be easily locatable, like a "What changes on Jan 1" page.    I think their webmaster works at UCLA making mazes for rats to try to run through and also uses them for flow chart modeling.

More specifically are they taking away face to face ammo sales?  Are the cops gonna bust down my door is I advertise ammo for sale and don't go through a dealer to sell it?

Face to Face is already gone, you need to transfer all ammo through an authorized ammo dealer since Jan 1 2018. Come 2019 you will need to perform a back ground check as well.

Edit to add. There is a lot still up in the air still, ammo permits, back ground check fees and maybe even waiting periods. The ballot had ammo permits, then the legislator passed a back ground check bill to overwrite it, the legality of that is questionable. Also the back ground check fee is $1 and instant, the CA DOJ is on record saying they can't do that and the feds have said that they wont help with ammo sales in that regard. If they can or not, get ready for some legal battles. Welcome to the party.

Sounds like I should sell this ammo before I get there December 20, or store it here

Yeah, the Communist Party.