Apart from LAX, SNA, ONT and LGB most traffic in the LA area is general aviation/flight training. To accommodate all that traffic and keep separation from the flows into the major airports it's always radar vectors and rarely any procedural flying. At some point you simply have to rely on ATC's altitude assignments for it to work. It can be very busy at times. Good local knowledge of terrain helps, even though it shouldn't be necessary. The MSA's are usually quite useless since many of them are in the order of 10-11000 ft, esp for bugsmashers. Due to the mountains north of LA. I second that ATC in the area, although good at "pushing tin", has annoying tendency to invent their own procedures. Often leaves pilots in the unknown.