Sounds like a fun trip!
I dont know too much about blues/roots clubs other than the House of Blues on Sunset, which doesnt always have blues groups
http://www.hob.com/venues/clubvenues/sunsetstrip/
but just going down Sunset would be fun as there is a lot to see; Mann Chinese Theatre, clubs, cars, etc.
Pomona Raceway (about 1 hour east of LA) will be having the Winternational drag races Feb. 9-12 with top fuelers and all the other big dogs. March 31- Apr 2 is the Super Chevy Show which always has a huge turnout of show cars and drag racing.
http://www.pomonaraceway.com/2006/schedule.html
Other races around the country I dont really know about, but here is the link to NHRA which should have their schedule of races on it
http://www.nhra.com/
Check this site out
http://www.weirdus.com/stories/CA00.asp they have all the odd legends and places to visit in Cali as well as the rest of the US (unfortunately they made a book and took a lot off their site so people will buy the book, which I did so if you have any questions, just ask). Going through Death Valley, you can find the "Moving Rocks" a place where enormous rocks have left a trail from movement over hundreds of years like they are in some kind of race. Kelso Dunes (about 30mi south of Baker) is home to singing dunes where, if you kick sand it sounds like someone is playing the Tuba...its strange. I dont know how much hiking, etc you want to do though.
If you are going up to Northern Cali, you can always stop at Laguna Seca, Monterey California. Here is their schedule
http://www.laguna-seca.com/events/
Chip Foose's shop is in Hunington Beach, about 45 min south of LA.
http://www.chipfoose.com/contact.aspx?LinkID=tn12 not sure where they film Overhaulin though, but I think its at his shop.
The Nethercutt collection is nice to see if you like really old cars. (Duesenburgs, Talbot-Lagos, Cord)
http://www.nethercuttcollection.org/index2.html There is over 100 cars there in damn near perfect shape plus art and strange musical instruments. NOTE: There are two buildings across the street from each other and the one (called San Sylmar) with about 20 cars, art, music is only open by reservation at select times, but its all free.
The Parnelli Jones museum is close to my house and I have been there on occasion, though im not sure if its open to the public or not and I dont think they have a website. There is about 10-15 of his old race cars and memorabilia there, I can find the address if you are interested.
There is also the Petersen Museum
http://www.petersen.org/ and if you are interested in going and can give me the date/time you want to go, I can probably get you into the elusive basement.
They are a lot of places around here to see in terms of hot rod builders, speed shops, etc. the only problem is going from one shop to the other in LA can take a LONG time cause of our crappy traffic.
Thats all I can think of right now, I will let you know if anything else comes to mind.