spazstic,
Where abouts are you in California, it's a big state. Initially I thought about getting a lower online, but I could find it at a local shop (this was back in March 2012) and it saved me the transfer fee and shipping. I think most places around me were charging $40.
For a bullet button, check out the Raddlock Bullet Button. You can make it so that when you are out of California you can convert to a regular mag release. Then before you cross the line, you use a simple, small flat head (or their supplied tool) to change it back to the CA compliant button.
As others have said, you don't need a bullet button at the time of purchase. I had my lower for several months before I installed it (I did it when I finally got the lower parts kit). All vendors do require that you have some kind of lock to take it out of their store, though.
If you live in San Diego, I can recommend a couple places (one is a regular poster here I believe). Actually, I can't think if any that are that bad and the selection is getting smaller. There's also a local company that makes their own down here. Turner's has been getting in quasi-regular shipments. One time they were getting in Palmetto State Armory. Lately they've had some off brand and have (in my opinion) charging too much for it.
I'm also new at this, haven't finished my first build. But I've been here and around this stuff for about 10 years now so I've picked up a bit. AR15.com, though, is the treasure trove.
R/Matel