well your kinda in for a bit of a culture shock, San Diego is one of the best places in my opinion to live in southern california. There are good places and bad places just like anywhere else inside of SD.
I dont know of any kart tracks that are down there, but i'm positive that there has to be some. If you want to travel about 60 miles north there is an excellent kart track and a halfway decent one. One is called Perris speedway in perris, ca. And the other (if still open) is called Adams raceway (i think) and is in Riverside, ca.
There is TONS of autocross events down here, its really really popular. There is something almost every weekend, and a lot of it seems to be down that way.
As for wheeling, its kind of a different world. We dont have ANY offroad parks anymore (that i know of). Everything is public use land, mainly desert in your area. I have not spent much time in SD wheeling, I seem to get distracted by the fine ladies and booze =)
If you head up north you'll find Big Bear, which is great for light wheeling in the summer and snow runs in the winter. The snow can add a bit of a challange and sometimes get you in trouble. But all in all there is not much challanging there unless you are semi-stock.
Calico is north east of Barstow and is one of my favorite places to wheel. Lots of sheer rock canyons and there is even some areas that can provide quite a challange at times for even the better equipped rigs.
Johnson Valley is about 30 miles north of big bear and is back into the desert. This is where all of the big boys go to play. There is more then a handful of excellent trails some easier then others that offer up all sorts of rig breaking fun. These trails are about as bad as it gets in the nation. You can search for some pics of some of the trails here.
I would recommend checking out
www.socalxj.com and joing up with that group to get a feel for the people. All in all the SD guys are a great bunch of guys, but we (people from the north of SD) dont get to wheel with them all that much since it is a bit of a drive.
Good luck on getting the job!